People v. Reeves (91 Cal. App. 4th 14, 2001)

Opinion

PARRILLI, J.

This appeal raises three challenges to the admissibility of statistical calculations based on DNA evidence. We conclude none of them has merit and that the procedures at issue have gained general acceptance in the scientific community.

A jury convicted appellant of several burglaries and sexual offenses committed against multiple victims during a nine-month period, and he was sentenced to 77 years in prison. With respect to two of the sex crimes charged, the jury heard forensic DNA evidence identifying appellant as the perpetrator. He challenges the admission of this evidence on appeal, claiming it should have been excluded pursuant to People v. Kelly (1976) 17 Cal.3d 24 [130 Cal.Rptr. 144, 549 P.2d 1240] (Kelly). Specifically, appellant argues: (1) the formula used by the California Department of Justice (DOJ) to calculate the statistical significance of DNA matches is not generally accepted in the scientific community because it fails to consider laboratory error rates; (2) the DOJ’s formula for calculating statistical significance of DNA matches determined by polymerase chain reaction (PCR) analysis is not generally accepted in the scientific community; and (3) the DOJ’s “fixed-bin” technique for determining the statistical probability of a DNA match violates correct scientific procedures because the bins are too small. Appellant claims the erroneous admission of DNA evidence deprived him of a fair trial and requires reversal.

Appellant also raises several “non-DNA” claims. He contends the evidence was insufficient to prove sexual battery in one charge and attempted robbery in another. He also claims the trial court erred in failing to instruct the jury sua sponte on lesser included offenses, with respect to the robbery convictions, and in calculating his sentence.

We conclude the trial court properly admitted the DNA evidence. However, the judgment must be modified to remedy minor instructional and sentencing errors.

Background

I. The Crimes

A. Sexual Assaults

1. Linda H.

One night in November 1993, 47-year-old Linda H. was home alone. She was not feeling well and went to bed in her clothes. She awoke around 5:30 a.m. to find an intruder leaning over her in the dark. He was holding a crowbar in one hand and pulling her bedside phone off the hook. He said, “Don’t make a sound, don’t look at my face, I don’t want to have to hurt you, ma’am.” He told Linda to roll over and then pulled her arm up behind her back so she could not move. He asked where Linda kept her jewelry, and she told him it was in the bathroom.

The intruder did not get up but began touching Linda’s buttocks and thighs over her clothes. When Linda repeated that her jewelry was in the bathroom, the man said, “come here” and pulled her face toward his unzipped crotch. “This is what I want,” he said, and pushed Linda’s head onto his erect penis. Linda said “oh no,” but the man shook the crowbar in a threatening way. He thrust his penis in and out of her mouth, still flexing and shaking the weapon. At one point, the man reached under Linda’s clothes and touched her breast. When she pushed his hand away, the intruder turned her over, pulled down her pants and underwear. He touched his penis to her genitals and attempted to enter her. To prevent this, Linda grabbed the man’s penis and masturbated him until he ejaculated into her hand.

Still holding the crowbar, the intruder forced Linda into the shower. He apologized, stating that God would punish him. He told Linda to wash her genital area thoroughly, with a lot of soap, and then told her to “stay there” while he walked toward the bedroom. After about 15 minutes, Linda ventured out of the shower and learned the intruder was gone. She later discovered her purse was missing from the house.

Linda described her attacker as Caucasian, between five feet seven and five feet nine inches tall, with a narrow waist and hips, strong hands and stubby fingers. Linda viewed two police lineups, in March 1994 and April 1996. At the first, held before appellant was a suspect, Linda felt “75 percent sure” one of the men was her attacker. At the second lineup, which included appellant, Linda noted that appellant and another suspect bore a strong physical resemblance to her attacker, but she could not positively identify either.

Police officers removed the stained bottom sheet from Linda’s bed. Forensic investigators determined the stain was seminal fluid, and, upon microscopic examination, they found sperm. The semen came from a donor with type O blood who was a secretor; the semen had a PGM (phosphoglucomutase) enzyme of type 1 plus, 1 minus. Appellant matched all these characteristics. Police also recovered two pubic hairs from the sheet. One appeared to be the victim’s, and the other resembled appellant’s pubic hair.

2. Carol B.

Carol B., a 45-year-old woman who lived alone, went to sleep at 11:00 p.m. on December 7, 1993. She woke to find an intruder standing by her bed. When she screamed, the intruder immediately covered her mouth and told her, “Don’t look at me, don’t scream. I won’t hurt you if you don’t scream.” Carol saw the man was holding a knife. She looked away and noticed her clock said it was 5:32 a.m. The intruder began fumbling with Carol’s miniblinds, eventually opening them and the bedroom window. He asked how old Carol was. She told him and then lied that she was very sick from cervical cancer, hoping that would scare him away. He replied, “Do you think you’re the only person in this room who’s sick?” Carol then heard clothes rustling, and when she turned she saw that the man’s pants were unzipped and his penis exposed. He told her to put her hand on it and “move it up and down,” which Carol reluctantly did. The intruder made Carol take off her shirt and forced her to orally copulate him. He ordered her not to spit anything out, and said “if you spit it out, it’s going to be all over for you.” When the man eventually ejaculated, Carol surreptitiously spit as much as she could into her hand and then wiped it onto her pillowcase. The man quickly dressed, closed the window and blinds, and ordered Carol into the shower. He told her to stay there while he looked around. When Carol emerged from the shower, she found the kitchen phone unplugged but was able to call police from a bedroom phone. She suffered a sore, bruised mouth from the attack, and she later discovered her purse had been taken.

Carol only saw her attacker briefly. She described him as Caucasian, in his late 20’s, around five feet eight or nine inches tall, weighing 140 to 150 pounds. He was physically fit but not large, and he had rough hands with stubby fingers. Carol attended both the 1994 and 1996 police lineups. She put question marks next to three of the suspects in the first lineup and one in the second lineup, but she could not positively identify anyone as her assailant.

The police discovered three latent fingerprints from Carol’s china cabinet. One of these, a partial print, matched appellant’s left index finger. Police investigators also examined Carol’s stained pillowcase. Because they could not readily determine whether the stains contained sperm, investigators sent the pillowcase to the DOJ’s DNA laboratory in Berkeley, California. This laboratory has the technical capacity to separate sperm cells from saliva and other cellular debris.

3. Janice B.

One night in February 1994, 56-year-old Janice B. went to sleep alone and was awakened by a man who was holding her shoulder and telling her to stay quiet. The man had a flashlight, and he spent some time searching the room for a gun or security alarm. When the intruder came back to Janice and unzipped his pants, Janice said “Oh dear God, please be with me now.” The man immediately zipped up his pants and asked Janice if she believed in God. She said she did and asked if he did too. When the man said “yes,” Janice asked him what he was doing there. He told her he had a lot of problems. Janice tried to talk with the man about his problems while they each smoked a cigarette. Janice told the man he seemed too smart to be ruining his life, and the man said she seemed “like a neat person.” But after they smoked, the intruder’s attitude changed. He began barking instructions and said he would hurt Janice if she did not do what he said. He told her to bring him her best pair of silky underwear. When she did so, the man unzipped his pants and masturbated himself with the panties. He told Janice to pull up her nightgown so he could look at her, and after a while he handed Janice the panties and said, “[y]ou know what to do.” She then masturbated him with the underwear. After he ejaculated, the intruder pulled down the bedding and scrubbed Janice’s bed with the panties. He then ordered Janice into the shower and told her to stay there while he looked through the house. At one point, he came back into the bathroom, reminded her that he knew who she was and where she lived, and threatened to come back if she told anyone about the incident. When she heard the intruder leave, Janice ran to the manager’s apartment and called the police. Along with the underwear her attacker had used, Janice noticed that some of her jewelry was missing, as was a decorative turquoise knife her son had made for her. Eighty dollars had been taken from her purse.

Janice described her attacker as Caucasian, well-spoken, around 25 years old, and about five feet eight or nine inches. She also viewed both the 1994 and 1996 police lineups, but could make no identification at either.

The police obtained one fingerprint lift from Janice’s apartment, but they could not make an identification based upon it. When investigators analyzed Janice’s sheet, they found some pubic hairs, which they determined were consistent with appellant’s. They recovered no semen from the sheet.

4. Debra E.

In June 1994, Debra E. lived with her roommate in a two-bedroom apartment. She was jerked awake one night by a man who was lying on top of her back and grabbing her hair and shoulder. The man said “Don’t scream and I won’t hurt you,” but Debra screamed as loud as she could. The intruder said, “Shut up or I’ll shoot you” and put something to her neck, but Debra discovered it was just the man’s finger. They struggled, and the man began to choke Debra. After she promised to be quiet and do what he wanted, the man slammed her face into the carpet and tied her wrists together with rope. Debra asked if he wanted to have sex with her, hoping he would do this instead of killing her, but the intruder said no, that was not what he wanted. He pushed her face into the carpet. When Debra struggled to get free, the intruder slammed his knee into her ribcage and struck her hard on the side of the head. Debra began screaming again, despite the intruder’s threat to use a knife on her and the extremely hard blows he dealt to both sides of her face and head. The assault was finally interrupted by police sirens. (Debra’s roommate, awakened by the screams, had called police from a pay phone outside, after discovering the phone in their apartment was dead.) The intruder ran out a sliding glass door. He was chased by police but evaded capture. Debra suffered multiple injuries from the assault, including trauma to her head, face, back and neck. Some things had been moved around in the apartment, and Debra’s roommate later discovered that her great grandmother’s engagement ring was missing from her jewelry box and a gold necklace she had left on the floor was gone.

Debra believed her attacker was Caucasian, about five feet seven to nine inches tall, and very strong. He had neck-length brown hair and rough hands that smelled like cigarettes. At the April 1996 lineup, Debra picked out appellant; however, she admitted she chose him based on having seen his photograph in the newspaper and had no independent recollection of his face.

The police recovered nylon cable, a plastic flex tie and a flashlight from Debra’s bedroom. A latent fingerprint lifted from one of the flashlight’s batteries matched appellant’s right index finger. Officers on the scene also found an abandoned bicycle, a discarded maroon sweatshirt, apparently worn by the intruder, and a screwdriver that had been used to pry open the sliding glass door of the apartment. Etched onto the screwdriver was the name “Harro Clifton.”

B. Burglaries

Ed Willis returned home from an overnight trip in October 1993 to find his home had been burglarized. Someone had pried open a sliding glass door and stolen, among other things, his collections of coins, knives and firearms.

On December 7, 1993, someone broke into Paul Clark’s apartment and stole a guitar and various pieces of jewelry.

In January 1994, Nigel Rees found his townhouse had been burglarized when he was away overnight. The intruder pried open a sliding door and stole cameras, clothing and some jewelry.

On May 12, 1994, the owner of Handlogger’s lumber business, Tim Mahoney, discovered his office had been broken into. The burglar took a rifle and a custom-built bicycle. Mahoney later identified the bicycle seized outside Debra E.’s apartment as his stolen property.

Kristine Bedford returned home from work one evening in June 1994 and found her house had been broken into through a sliding glass door. Missing were some jewelry, camera equipment, a case of silverware and a leather jacket.

Dorothy Castle’s townhouse was burglarized on June 25, 1994, while she was asleep. The burglar stole cash from her purse, a box of silverware, jewelry and some bonds and stock certificates.

Following up on the “Harro Clifton” screwdriver found at the Debra E. crime scene, police officers began investigating this individual. They learned Clifton owned a warehouse in connection with his work as an electrical contractor. He moved much of his personal property into this warehouse in 1993, when he separated from his wife. Clifton shared the warehouse space with three other men, who also ran businesses out of the warehouse. These men and their partners had keys to the building, as did Clifton’s brother, sister and receptionist. Many people, including appellant, had access to the building.

Clifton had known appellant since they were children. In the fall of 1993, appellant asked Clifton if he could store some things in the warehouse. Appellant also slept at the warehouse sometimes, though Clifton discouraged it. Generally, appellant slept in an outdoor area, but he kept his things at the warehouse. In January 1994, Clifton moved to San Francisco and gave appellant a key to the warehouse.

When police first visited Clifton’s warehouse, which was about a quarter mile from Debra E.’s apartment, they noticed several flex ties like the one found at the Debra E. crime scene. In a search of the warehouse, police discovered: a semiautomatic pistol; a manual for an Intertec 9 semiautomatic weapon, which was identified by Ed Willis; a chess set with velvet interior and magnetic pieces, later identified by Linda H. and her two daughters; jewelry and a decorated turquoise knife, identified by Janice H.; a silverware set, identified by Dorothy Castle; a watch and pin, identified by Nigel Rees; a Taylor guitar, identified by Paul Clark; inside the guitar case, three items of jewelry, identified by Kristine Bedford; and additional jewelry and camera equipment taken from Bedford’s home.

II. The DNA Evidence

The DOJ laboratory tested semen recovered from the Linda H. and Carol B. crime scenes using the two basic methods of DNA analysis: RFLP and PCR. Appellant’s DNA profile (determined from a blood sample) matched the DNA from semen at both crime scenes at every site tested.

In the Linda H. case, PCR testing of the types “DQ-alpha” and “D1S80” showed a match for appellant, and caused the DOJ to exclude another man who was first considered a suspect. The DOJ also found a match between appellant’s DNA and semen from the bed sheet at 10 different sites, or “loci,” using RFLP analysis. Criminalist Gary Sims compared the results at six of the well known loci to DNA population databases and, using a statistical formula called the product rule, found that the probability such a match could occur at random was very small. He determined the DNA profile would occur in only 1 in 54 billion Caucasians, 1 in 170 billion African-Americans, and 1 in 180 billion Hispanics. Since there are only six billion people on earth, this six-loci profile is extremely rare.

Semen extracted from Carol B.’s pillowcase was also examined. A criminalist working under Sims’s supervision found a four-loci match between appellant’s DNA and DNA from the evidence sample using RFLP analysis. The probability of this result occurring at random was 1 in 7.7 million for Caucasians, 1 in 26 million for African-Americans, and 1 in 17 million for Hispanics. PCR testing of the DQ-alpha and polymarker types also showed a match between the DNA in appellant’s blood and in semen from the crime scene. The probability of this result, calculated by the product rule, was 1 in 500,000 Caucasians, 1 in 11 million African-Americans, and 1 in 260,000 Hispanics.

Appellant made a pretrial motion to exclude all DNA evidence on the ground that it did not satisfy the criteria for admissibility under Kelly, supra, 17 Cal.3d 24.

A. Overview of DNA Analysis

Previous opinions of this court (People v. Barney (1992) 8 Cal.App.4th 798 [10 Cal.Rptr.2d 731] (Barney)) and the Supreme Court (People v. Venegas (1998) 18 Cal.4th 47 [74 Cal.Rptr.2d 262, 954 P.2d 525] (Venegas)) have discussed in some detail the science of forensic DNA analysis. We summarize the important principles again here, because the bulk of appellant’s claims concern the scientific validity of the DNA evidence linking him with the Linda H. and Carol B. sexual assaults.

DNA is the genetic material found in the nucleus of virtually all human cells except red blood cells. It is organized into 23 pairs of chromosomes, one chromosome in each pair being inherited from the mother and one from the father. (Nat. Research Council, The Evaluation of Forensic DNA Evidence (1996) pp. 60-61 (hereafter 1996 NRC Report).) “A chromosome is a long DNA molecule in the shape of a spiral staircase. [Citation.] ‘It consists of two parallel spiral sides (i.e., a double helix) composed of repeated sequences of phosphate and sugar. The two sides are connected by a series of rungs, which constitute the steps in the staircase. Each rung consists of a pair of chemical components called bases. There are four types of bases— adenine (A), cytosine (C), guanine (G), and thymine (T). A will pair only with T, and C will pair only with G.’ [Citation.] There are over 3 billion base pairs in the 46 chromosomes of a single human cell.” (Venegas, supra, 18 Cal.4th at pp. 58-59.)

“In most portions of DNA, the sequence of base pairs is the same for everyone. Those portions are responsible for shared traits such as arms and legs. In certain regions, however, the sequence of base pairs varies from person to person, resulting in individual traits. A region—or locus—that is variable is said to be polymorphic. In some polymorphic loci, at fragments called alleles, short sequences of base pairs repeat for varying numbers of times. These are called variable number of tandem repeat (VNTR) sequences.” (Barney, supra, 8 Cal.App.4th at p. 806.) Forensic scientists have developed two procedures to identify individuals through variations in the base-pair sequences at polymorphic DNA loci: RFLP and PCR. (Venegas, supra, 18 Cal.4th at p. 58, fn. 6.)

1. RFLP Processing and Matching Procedures

RFLP analysis focuses on the highly variable VNTR loci. The variability of these regions “is what makes DNA analysis possible. In effect, the lengths of sets of multiple (usually eight) polymorphic fragments (or VNTR alleles) obtained from a suspect’s DNA and from crime scene samples are compared to see if any sets match, and a match is accorded statistical significance.” (Barney, supra, 8 Cal.App.4th at p. 806.)

DNA from a sample and from a suspect must be processed to allow comparison. First, DNA is extracted from bodily material. (Barney, supra, 8 Cal.App.4th at p. 806.) Second, the “extracted DNA is ‘cut’ into thousands of fragments at specific points by application of restriction enzymes. The restriction enzymes act as ‘chemical scissors’ in that they sever the DNA at targeted base-pair sites.” (Ibid.) Third, in a process called electrophoresis, the DNA fragments are separated according to their base-pair size. “The various sample fragments being tested are placed in separate lanes on one end of a gel slab and an electrical current is applied, causing the fragments to move across the gel. Shorter fragments move farther than longer fragments. Thus, at the completion of electrophoresis, the sample fragments are arrayed across the gel according to size. [^] In addition to the sample fragments, other fragments called size markers, which have known base-pair lengths, are placed in separate lanes on the gel in order to facilitate measurement of the sample fragments.” (Id. at pp. 806-807.) Fourth, through a process called “Southern transfer,” the DNA fragments are denatured and wicked from the gel onto a nylon membrane. (Id. at p. 807.) The fifth and sixth steps allow the DNA fragments to be visualized on X-ray film. Through hybridization, radioactive single-strand DNA probes are applied to the nylon membrane, where they seek out and bind themselves to denatured DNA fragments that have complementary base sequences. (Venegas, supra, 18 Cal.4th at p. 61.) Then, when the membrane is washed and exposed to X-ray film, a pattern of bands appears depicting DNA fragments at each locus probed. (Id. at pp. 61-62.) “The location of a band on the X-ray film indicates the distance a fragment traveled as a result of electrophoresis, and hence the length of the fragment. The size-marker fragments also appear on the films, enabling measurement of the base-pair lengths of the sample fragments. [^[] The end result of the processing substeps is a picture of a person’s DNA pattern (which may be produced by overlaying the four X-ray films).” (Barney, at p. 808.) The X-ray film is called an autoradiograph, or autorad. (Id. at p. 807.)

Next, scientists compare the autorads to see if the suspect’s DNA pattern matches that produced by DNA from the evidence sample. “First, the patterns are visually evaluated (i.e., ‘eyeballed’) to determine whether there is a likely match. Most exclusions will be obvious, since the patterns will be noticeably different. If there is not an obvious exclusion, the bands in the patterns are subjected to computer-assisted analysis to determine the length of the represented DNA fragments as measured in base-pair units. The measurements are taken by comparing the bands for the sample fragments with the bands for the size-marker fragments of known base-pair lengths.” (Barney, supra, 8 Cal.App.4th at p. 808.)

“Because of inherent limitations in the DNA processing system, it is not possible to obtain exact base-pair measurements of the sample DNA fragments. For that reason, forensic laboratories have developed DNA match criteria based on the variations they have experienced in repeated measurements of DNA from the same source. Those criteria determine the ‘match window’—or range of sizes—constructed around each band for purposes of declaring a ‘match.’ For example, under the FBI’s match criterion of plus or minus 2.5 percent, the window around a band that measures 1,000 base pairs is from 975 to 1,025 base pairs. If the window of either band, or a single band, on one sample fails to overlap the window of the corresponding band on another sample, there is an exclusion of any match between the samples. If the windows of both bands, or of the single bands, of each sample overlap, there is a match at the locus disclosed by that probe.” (Venegas, supra, 18 Cal.4th at pp. 62-63.) The window surrounding each individual band is called an “uncertainty window,” and the window that results from the combination of two bands that overlap is called a “match window.” (1996 NRC Rep., supra, at pp. 19-20.) Although some conditions adverse to reliability may make match results inconclusive at a given locus, such a determination “does not invalidate matches at the other loci.” (Venegas, at pp. 62-63.)

If the bands at any locus do not match, the suspect is excluded as a possible donor of the sample DNA. However, “if all of the suspect’s fragment lengths are the same as the crime scene fragment lengths within the margin of error—i.e., if the band patterns produced by the processing step are identical—a match is declared.” (.Barney, supra, 8 Cal.App.4th at p. 809.)

2. PCR Processing and Matching Procedures

PCR is a molecular biology technique that copies or amplifies small pieces of DNA by a process similar to DNA’s own self-replicating properties. (People v. Morganti (1996) 43 Cal.App.4th 643, 662 [50 Cal.Rptr.2d 837] (Morganti); 1996 NRC Rep., supra, at p. 69.) It has been likened to a “genetic photocopy machine” (U.S. v. Lowe (D.Mass. 1996) 954 F.Supp. 401, 409), and is often employed when the DNA sample available is too small or degraded to produce good results using RFLP. (Morganti, at p. 662.)

PCR forensic analysis involves three steps. First, DNA is extracted from cells in the sample. Second, select regions of the DNA are amplified. Scientists have identified these regions, also referred to as genes or genetic markers, as areas that exhibit great genetic variation among the population. One widely used marker is the DQ-alpha gene. (1996 NRC Rep., supra, at p. 23.) On average, only about 7 percent of the population shares the same DQ-alpha type. (Ibid.) Like DQ-alpha, the D1S80 locus is used in PCR testing because it contains several alleles and exhibits great variation. (Id. at p. 72.) Polymarker analysis, which amplifies several loci simultaneously, has also been validated for use in PCR testing. (Ibid.) After amplification, in the third and final step of PCR analysis the amplified gene is “typed,” through the use of DNA probes, to identify the specific alleles it contains. (Morganti, supra, 43 Cal.App.4th at p. 662.) If the DNA profile thus constructed differs in any way between the suspect and the sample, the suspect is excluded. But if the profiles match, the analyst must next determine how common the profile is in the population.

3. Determining Statistical Significance of a Match

Procedures for determining the statistical significance of a match vary depending on whether the match derives from RFLP or PCR testing. Most PCR-based procedures allow alleles to be identified, and compared, as discrete entities; therefore, PCR usually does not entail the same measurement uncertainties as are encountered in RFLP analysis of VNTR fragments. (1996 NRC Rep., supra, at p. 70.) Essentially, this means that an additional step, called “binning,” is required in an RFLP statistical analysis.

a. RFLP Binning Procedures

Once a match of a given base-pair size has been found at a certain locus, the next question is how frequently that size occurs at that locus in the general population. In other words, how commonly are DNA bands of a certain size found in this region? “This is accomplished by assigning each band to a category comprising a definite range of base-pair lengths—called a bin—and then determining how often bands within that bin appear in a data base composed of persons of a given race.” (Barney, supra, 8 Cal.App.4th at p. 809.)

There are two types of bins: floating and fixed. “A floating bin, constructed for each forensic comparison, is a range of sizes at least as large as the match window, centered on the measured size of the evidentiary band in question. The evidentiary band’s frequency, i.e., the probability of its appearing in the DNA profile of a randomly selected member of the population underlying the database, is calculated from the ratio of the number of bands in the bin to the total number of bands in the database for that locus.” (Venegas, supra, 18 Cal.4th at pp. 64-65.)

“Fixed bins, on the other hand, compartmentalize the entire spectrum of VNTR base-pair sizes likely to appear as bands on an autorad. The spacing of the fixed-bin boundaries is somewhat uneven because, like the bands in the autorad’s sizing-ladder lanes, they are derived from viral DNA that has been exactly measured. A separate fixed-bin table is compiled for each locus in each database. Each database band is entered within the bin that encompasses its base-pair size. To protect a suspect against unduly small frequencies, any bin with four or fewer bands is combined with its neighbor until each bin contains a minimum of five bands. The fixed-bin table shows not only each bin’s range of sizes and number of bands, but also each bin’s frequency, which is calculated from the ratio of the number of bands in the bin to the total number of bands in the table. (See 1996 NRC Rep., supra, [at] pp. 97, 143; Budowle et al., Fixed-Bin Analysis for Statistical Evaluation of Continuous Distributions of Allelic Data from VNTR Loci, for Use in Forensic Comparisons (1991) 48 Am. J. Hum. Genetics 841, 846 [citing an example in which a table of 31 bins, ranging from 0 to over 12,000 base pairs, was collapsed into a table of 23 bins].) ft[] In fixed-bin analysis, the frequency of an evidentiary band is determined by assigning it the frequency of the fixed bin into which its base-pair size falls.” (Venegas, supra, 18 Cal.4th at p. 65.)

In view of the measurement uncertainties of RFLP, analysts include an uncertainty window around DNA bands produced by the evidence sample and the suspect’s sample. Whereas the FBI uses an uncertainty window of 2.5 percent around each band (1996 NRC Rep., supra, at p. 19), the DOJ uses a window of plus or minus 1.8 percent. As discussed, a “match” is declared when the uncertainty windows of the evidence and suspect bands overlap. The “match window” that is then compared to population frequency tables may be defined in different ways. Based on the FBI’s uncertainty window of 2.5 percent, the NRC defines the match window as the evidence band’s measurement with 5 percent of its value added and subtracted—for a total match window of 10 percent around the evidence band. (Id. at p. 20.) By contrast, the FBI defines the match window to be the window formed by the union of the 5 percent-wide evidence window and the 5 percent-wide suspect window. {Id. at p. 144; see also Venegas, supra, 18 Cal.4th at p. 64, fn. 16.) Thus, the FBI’s match window—i.e., the range of values it compares to a population frequency database—is no larger than 10 percent wide and may be smaller.

Where the match window overlaps multiple fixed bins, the DOJ, like the FBI, assigns the match to the fixed bin with the highest probability. The 1996 NRC Report recommends this procedure, although a 1992 report (NRC, DNA Téchnology in Forensic Science (1992) (hereafter 1992 NRC Report)) recommended that the frequencies of all overlapped bins be added together. (1996 NRC Rep., supra, at p. 144; Venegas, supra, 18 Cal.4th at p. 65, fn. 18.)

b. Mathematical Calculations: the Product Rule

The final step in both RFLP and PCR analysis requires the analyst to calculate the statistical probability that the DNA profile of a person, selected at random from the relevant population, would contain the same pattern of alleles represented in the evidence sample. (Venegas, supra, 18 Cal.4th at p. 65.) In RFLP, bands at each locus have been assigned to fixed bins, each of which is known to contain alleles that occur at certain frequencies in population databases specific to Caucasians, African-Americans and Híspanles. Databases have also been developed to determine population frequencies of the various alleles that may be detected using PCR. (1996 NCR Rep., supra, at pp. 117-119.)

Once population frequencies have been determined for each locus, the analyst must calculate the probability that a person at random would have the same combination of matches at all loci. “The most straightforward means of making this calculation is through application of the ‘product rule.’ ” (Venegas, supra, 18 Cal.4th at p. 65.) “The essence of the product rule is the multiplication of individual band probabilities to arrive at an overall probability statistic expressed as a simple fraction, such as 1 in 100,000.” (Id. at p. 66.) Thus, the product rule is simply the multiplication of the frequencies found at each locus studied. The result is a probability statistic that reflects the overall frequency of the complete DNA profile. It is often quite small. (Ibid.)

B. The Kelly Hearing

The trial court in this case held a five-day evidentiary hearing pursuant to Evidence Code section 402 and Kelly, supra, 17 Cal.3d 24, to determine the admissibility of DNA evidence against appellant. As a preliminary matter, the court found that the first stages of DNA analysis, i.e, “the science of typing and matching genetic factors,” had gained general acceptance in the scientific community and were admissible under Kelly. The court therefore confined the issues at the hearing to: (1) the general acceptance of statistical analyses used to determine the significance of matching DNA profiles; and (2) the propriety of testing methods employed in this case.

1. Prosecution Expert Testimony

a. Julian Adams

Dr. Julian Adams, a population geneticist at the University of Michigan, addressed the DOJ’s RFLP statistical calculations and the RFLP measuring and matching process in general. Adams testified that the NRC includes some of the most respected scientists in the country and, along with the National Academy of Sciences, is responsible for advising the government on scientific issues. He was familiar with the NRC’s 1992 and 1996 Reports on DNA evidence, and he opined that the procedures outlined in the 1996 NRC Report for the statistical evaluation of RFLP matches are generally accepted within the scientific community.

In Adams’s opinion, it is scientifically appropriate to use the product rule to determine the statistical significance of an RFLP match, even though the rule was criticized in the past for failing to account adequately for the possibility of substracturing within populations. Some scientists have argued the FBI’s three population databases are too homogenous and can produce misleading frequency data for such subgroups. (See 1996 NCR Rep., supra, at pp. 28, 99-104.) To address this concern, authors of the 1992 NRC Report developed mathematical modifications of the product rule called the “ceiling principle” and “interim ceiling principle,” which essentially placed lower limits on the frequency values that could be reported. (Id. at p. 35.) However, in 1996 the NRC concluded that sufficient data had accumulated to show that neither ceiling principle is necessary, and the 1996 NCR Report therefore endorsed use of the unmodified product rule. (Id. at pp. 35, 38; see also Soto, supra, 21 Cal.4th 512, 540.)

Adams was “very impressed” with the DOJ laboratory’s procedures and attention to detail, and he thought there was not a better DNA testing lab in the country. In this case, the DOJ used scientific procedures that were correct and even more conservative than those recommended by the NRC. The defense attempted to cross-examine Adams about the rate of “false-positive” errors in DNA laboratories across the country; however, the trial court sustained relevance objections to most of this questioning. Adams agreed with the 1996 NRC Report’s conclusion that it is not appropriate to factor an “average error rate” into DNA profile frequency calculations, because accurate lab error rates are too difficult to determine and laboratories may vary widely in their proficiencies. Moreover, all laboratories now undergo extensive proficiency testing, and procedures to protect against error have greatly improved over past years. The proper way to address any continuing concern over laboratory errors, Adams opined, is to split samples and allow testing by different laboratories.

On cross-examination, the defense questioned whether the DOJ’s fixed-binning procedures could lead to statistical errors, because some of the fixed bins were smaller than the potential match windows. The defense argued the use of such undersized bins would lead to improperly low estimates of population frequencies. Adams was not familiar with the article that formed the basis of this argument (Fung, 10% or 5% Match Window in DNA Profiling (1996) 78 Forensic Sci. Internat. Ill (hereafter Fung)), but he thought any problem with small bins would be resolved by the FBI (and DOJ) procedure of combining fixed bins that have very rare frequencies.

b. Charlotte Word

Dr. Charlotte Word, a molecular biologist at the private laboratory Cell-mark Diagnostics in Maryland, testified about her review of the DOJ laboratory’s testing procedures, primarily in regard to PCR. Word discussed how PCR testing is done in general and the particular results of PCR analysis in the Carol B. case, which found matching alleles at seven separate loci. She explained that the DOJ calculated the significance of this match by looking up the population frequencies of each of the seven alleles and then multiplying them together pursuant to the product rule.

Word confirmed that the product rule is generally used throughout the forensic community to assess the statistical significance of PCR-based tests, and she cited the NRC’s conclusion that the statistical preconditions for use of the product rule, which have been proven for RFLP, are also true for PCR. (1996 NRC Rep., supra, at pp. 35, 119.) These preconditions are “Hardy-Weinberg equilibrium” and “linkage equilibrium.” Hardy-Weinberg equilibrium means that, at a particular genetic locus, alleles are inherited independently of each other, such that the presence of one allele is not correlated with any other allele at that locus. (Venegas, supra, 18 Cal.4th at pp. 66-67; 1996 NRC Rep., supra, at pp. 90-92.) Linkage equilibrium means that alleles at different genetic loci are independent, such that an allele at one locus is not correlated with the presence of a certain allele at another locus. (Venegas,, at p. 67; 1996 NRC Rep., supra, at p. 106.) According to Word, studies have shown that the regions examined in the DOJ’s PCR testing satisfy Hardy-Weinberg and linkage equilibrium. She knew of no published article disagreeing with application of the product rule to these PCR loci, nor of any controversy in the scientific community about use of the product rule in PCR analysis in general.

Word reviewed the RFLP and PCR testing done in this case and confirmed that the DOJ performed both in accordance with generally accepted and reliable scientific protocols. The trial court sustained relevance objections when the defense attempted to cross-examine Word about the history of laboratory errors at her facility, Cellmark. Word was not aware of any laboratory errors ever occurring in forensic DNA analysis at the DOJ lab. She observed that the laboratory is accredited by the American Society of Crime Laboratories Directors and therefore has submitted its procedures to intense scrutiny through, for example, proficiency testing and on-site inspections.

c. Gary Sims

Gary Sims, a supervising criminalist at the DOJ laboratory, testified in general about the lab’s accreditation and quality assurance protocols and also addressed the specific testing done in the Linda H. and Carol B. cases. Sims explained that most of the DOJ’s testing protocols are based on procedures developed by the FBI. In RFLP analysis, the DOJ will declare a match only when the evidence and suspect bands fall within “a plus or minus 1.8 percent match window.” The lab then uses the FBI’s fixed bin methodology to determine population frequencies and applies the unmodified product rule to complete the statistical analysis. Sims testified that, no matter which formula was applied to determine statistical significance, an RFLP match seen across multiple loci is exceedingly rare. The DOJ also uses the unmodified product rule in PCR analysis. Sims knew of no published article criticizing the use of the product rule to calculate PCR-based statistics.

Sims stated that DNA analysts at the DOJ laboratory undergo proficiency testing twice a year. He also confirmed that evidence samples from each of the cases had been split, so that they could be retested by the defense. Once again, the trial court sustained relevance objections to defense questions concerning previous laboratory errors committed at the DOJ laboratory or by Sims or other analysts who worked with him. The court reasoned that the only relevant errors were errors committed in this case.

2. Defense Expert Testimony

The defense presented only one witness at the Kelly hearing: Dr. Laurence Mueller, a professor of ecology and evolutionary biology at the University of California, Irvine. Mueller testified to his opinion that a controversy exists in the scientific community concerning the propriety of using the unmodified product rule in RFLP analysis. Our Supreme Court has since disagreed in Soto, supra, 21 Cal.4th 512, and appellant has withdrawn this claim on appeal. However, we summarize Mueller’s attack on the product rule insofar as it remains relevant to a PCR analysis.

First, Mueller argued that the product rule is statistically invalid due to the existence of population subgroups. Although a 1992 analysis of the FBI’s DNA database concluded that the database satisfied Hardy-Weinberg and linkage equilibrium principles (Weir, Independence of VNTR Alleles Defined as Fixed Bins (1992) 130 Genetics 873; Weir, Independence of VNTR Alleles Defined as Floating Bins (1992) 51 Am. J. Hum. Genetics 992), Mueller asserted that a reanalysis of the data from Weir’s study found compelling evidence of two-locus associations. (Slimowitz & Cohen, Violations of the Ceiling Principle: Exact Conditions and Statistical Evidence (1993) 53 Am. J. Hum. Genetics 314.) Such a finding indicates a departure from linkage equilibrium. According to Mueller, another study of the FBI’s database found numerous departures from Hardy-Weinberg equilibrium at certain regions of RFLP analysis. (Geisser & Johnson, Testing Independence of Fragment Lengths Within VNTR Loci (1993) 53 Am. J. Hum. Genetics 1103.) Finally, Mueller cited a letter to the journal Nature that he coauthored in response to a 1994 article that proclaimed the controversy over DNA evidence to be over. (Lander & Budowle, DNA Fingerprinting Dispute Laid to Rest (Oct. 27, 1994) 371 Nature 735 (hereafter Lander & Budowle).) The letter, which was signed by 27 university scientists (including Mueller), asserted that the effect of population subgroups on frequency calculations remained a continuing cause for concern. However, this letter was never published, and Mueller could only confirm that two of the signers still held the same views.

With regard to use of the product rule in PCR analysis, Mueller claimed some published results were “beginning to be seen, at least in [his] mind” that contradicted the assumptions of allele independence. The two articles Mueller relied on for this opinion reached a contrary conclusion, however, finding that all of the PCR loci used in the present case satisfied Hardy-Weinberg and linkage equilibrium expectations. (Budowle et al., Validation and Population Studies of the Loci LDLR, GYP A, HBGG, D7S8 and Gc (PM Loci), and HLA-DQ( Using a Multiplex Amplification and Typing Procedure (1995) 40 J. Forensic Sci. 45 (hereafter Budowle, Lindsey); Hochmeister et al., Swiss Population Data on the Loci HLA-DQ, LDLR, GYPA, HBGG, D7S8, Ge and D1S80 (1994) 67 Forensic Sci. Intemat. 175.) Nevertheless, Mueller claimed he found departures from independence at two loci when he examined the data underlying these studies. Mueller also criticized the PCR databases as being too small to permit testing of the Hardy-Weinberg and linkage equilibrium assumptions with sufficient statistical power. He named Donald Barry, a statistician at Duke University, as someone who agreed with this criticism, yet the defense offered no further evidence about Barry or any published scientific work supporting his point of view.

In short, Mueller disagreed with the 1996 NRC Report concerning use of the unmodified product rule. Instead, he advocated either the ceiling principle (as proposed in the 1992 NRC Rep.) or a formula called the counting method. Mueller also contended that any statistical calculation should be modified by the testing laboratory’s rate of errors or “false positives.” Thus, if testing showed a DNA profile match with an expected frequency of 1 in millions, but the lab had a false positive “error rate” of 1 in 1,000, Mueller would report only the larger, laboratory error statistic. Again, Mueller acknowledged that the 1996 NRC committee rejected this idea. He was not aware of any errors committed by the DOJ in connection with the DNA testing in this case.

Relying on the 1994 Fung article concerning the size of the FBI’s fixed bins, Mueller observed the DOJ’s fixed bins may also be too small to accommodate a match window that can be up to 7.2 percent wide (i.e., the size of the evidence band, plus or minus 3.6 percent). He contended the only solution to this sizing problem was to add the frequencies of all bins overlapped by a match window—a procedure the 1992 NRC Report suggested but the 1996 report abandoned. (1996 NRC Rep., supra, at p. 20.) Mueller acknowledged that the DOJ had followed all statistical computation procedures outlined in the 1996 NRC Report.

On March 3, 1998, the trial court denied appellant’s motion to exclude DNA evidence. Relying largely on the 1996 NRC Report, the court found the unmodified product rule had gained general acceptance in the scientific community, both for RFLP and PCR analysis. The court rejected the defense contention that the probability calculations must be modified by a laboratory error rate, reasoning “that issue is really not an issue related to the science but related to the scientist. It seems that if a lab error should occur, then none of the probabilities have any scientific basis . . . .” The court further observed that it found Dr. Mueller’s analysis to be biased and not entirely credible. Finally, noting the defense had raised issues about the DOJ’s laboratory procedures, the court stated: “no evidence was produced to show that there was any departure from the generally accepted procedures in the scientific community . . .

Discussion

I. Admissibility of the DNA Evidence

In Kelly, supra, 17 Cal.3d 24, the Supreme Court established a three-part test for the admissibility of evidence derived from a new scientific technique, such as DNA profiling. First, “the reliability of the method must be established, usually by expert testimony.” (Id. at p. 30, italics omitted.) “Reliability” means the technique is “ ‘sufficiently established to have gained general acceptance in the particular field in which it belongs.’ ” (Ibid., italics omitted, quoting Frye v. United States (D.C. Cir. 1923) 293 Fed. 1013, 1014, 34 A.L.R. 145.) Second, “the witness furnishing such testimony must be properly qualified as an expert to give an opinion on the subject.” (Kelly, at p. 30, italics omitted.) And, third, “the proponent of the evidence must demonstrate that correct scientific procedures were used in the particular case.” (Ibid.; see also Venegas, supra, 18 Cal.4th at p. 78.)

A. General Acceptance of Unmodified Product Rule

Appellant raises two arguments on appeal that he characterizes as “prong-one” Kelly challenges. He contends the unmodified product rule lacks general acceptance in the scientific community for PCR analysis due to problems caused by population subgroups and the relatively small size of PCR databases. He also argues that the product rule, as applied to both RFLP and PCR testing, has not gained general acceptance because a controversy remains as to whether the rule should be modified to account for laboratory error rates.

“‘ General acceptance’ under Kelly means a consensus drawn from a typical cross-section of the relevant, qualified scientific community.” (People v. Leahy (1994) 8 Cal.4th 587, 612 [34 Cal.Rptr.2d 663, 882 P.2d 321] (Leahy).) “The Kelly test does not demand ‘absolute unanimity of views in the scientific community .... Rather, the test is met if use of the technique is supported by a clear majority of the members of the community.’ ” (Venegas, supra, 18 Cal.4th at p. 85, quoting People v. Guerra (1984) 37 Cal.3d 385, 418 [208 Cal.Rptr. 162, 690 P.2d 635].) It is settled that the product rule, as a relatively new statistical methodology, is subject to “Kelly screening” to assure both its general acceptance and its correct application. (Venegas, at p. 84; Soto, supra, 21 Cal.4th at pp. 518-519.)

On appeal, “ ‘general acceptance’ ” is considered “a mixed question of law and fact subject to limited de novo review.” (People v. Reilly (1987) 196 Cal.App.3d 1127, 1134 [242 Cal.Rptr. 496].) Thus, “we review the trial court’s determination with deference to any and all supportable findings of ‘historical’ fact or credibility, and then decide as a matter of law, based on those assumptions, whether there has been general acceptance.” (Id. at p. 1135.) Ordinarily, an appellate court will confine its review under Kelly to evidence contained in the trial record, but the court may also consult decisions from other jurisdictions on the issue of whether a technique has met with consensus among scientists. (Id. at pp. 1134-1135; People v. Brown (1985) 40 Cal.3d 512, 533-535 [230 Cal.Rptr. 834, 726 P.2d 516], reversed on another ground in California v. Brown (1987) 479 U.S. 538 [107 S.Ct. 837, 93 L.Ed.2d 934].)

1. Use of Product Rule in PCR Analysis

In Soto, supra, 21 Cal.4th 512, the Supreme Court soundly rejected one of appellant’s original claims on appeal, i.e., that use of the unmodified product rule was not validated by general consensus within the scientific community. After a detailed summary of expert testimony presented at two Kelly hearings and at trial, Soto discussed the decision in People v. Axell (1991) 235 Cal.App.3d 836 [1 Cal.Rptr.2d 411], which confirmed general scientific acceptance of the product rule, and this court’s 1992 decision in Barney, supra, 8 Cal.App.4th 798, which concluded subsequent publications had undermined the rule’s acceptance. (Soto, at pp. 526-537.) The court then reviewed significant developments after Barney, including: (1) a 1993 FBI publication of a worldwide study of VNTR frequency data, which concluded the unmodified product rule was reliable and free from error due to population substructuring (IA FBI, VNTR Population Data: A Worldwide Study (1993)); (2) a 1994 article in which Dr. Eric Lander, formerly a leading opponent of the product rule, concluded the rule offered “a reasonable best estimate” of random match probabilities (Lander & Budowle, supra, 371 Nature at pp. 737-738); (3) publication of the 1996 NRC Report, which reexamined the statistical issues and explicitly approved use of the product rule (1996 NRC Rep., supra, at pp. 2-4, 122); and (4) a collection of articles, authored largely by defense expert witnesses, which criticized the 1996 NRC Report but expressed no disagreement with the product rule (e.g., Lempert, After the DNA Wars: Skirmishing with NRC II (Summer 1997) 37 Jurimetrics J. 439). (Soto, at pp. 537-539.)

The Supreme Court then observed that a majority of other states “have concluded that the controversy over population substructuring and use of the unmodified product rule has been sufficiently resolved,” and “extensive literature” had developed in peer-reviewed scientific journals to show that population substructuring does not significantly impact frequency estimates using the product rule. (Soto, supra, 21 Cal.4th at pp. 540-541.) The court therefore concluded: “It is clear from the evidence in the record, the clear weight of judicial authority, and the published scientific commentary, that the unmodified product rule, as used in the DNA forensic analysis in this case, has gained general acceptance in the relevant scientific community and therefore meets the Kelly standard for admissibility.” (Id. at p. 541.)

Respondent reads this decision broadly as an endorsement of all applications of the product rule; however, appellant correctly points out that Soto concerned only RFLP analysis, not PCR. No challenge was ever raised or considered in Soto to use of the product rule with PCR databases. Moreover, the court discussed scientific articles that analyzed the independence of VNTR alleles, and it cited no scientific conclusions specific to PCR markers. (See Soto, supra, 21 Cal.4th at pp. 538-539.) Thus, while Soto’s discussion of the population substructure issue is informative, it does not settle the question with respect to PCR analysis. (See San Diego Gas & Electric Co. v. Superior Court (1996) 13 Cal.4th 893, 943 [55 Cal.Rptr.2d 724, 920 P.2d 669] [“Cases are not authority ... for issues not raised and resolved.”].)

Nor do we consider the appellate court decisions in Morganti, supra, 43 Cal.App.4th 643, and People v. Wright (1998) 62 Cal.App.4th 31 [72 Cal.Rptr.2d 246], to be controlling because neither case involved a Kelly challenge to the product rule. The defendant in Morganti challenged PCR typing and matching methodology as well as PCR-based “statistical evidence” (Morganti, at p. 669), but the court had no occasion to consider the product rule because the PCR testing was done for only one gene, DQ-alpha. (Id. at p. 662.) Thus, the frequency of the defendant’s DQ-alpha genotype (one in twenty-two Caucasians) was not multiplied by anything. (See id. at p. 669.) In Wright, the defendant apparently did not raise a challenge under Kelly to use of the product rule in calculating the frequency of his PCR profile. Instead, he complained this statistical analysis violated his right to due process—an argument the court rejected. (People v. Wright, supra, at pp. 43-44.) The Wright court did not address the question of the product rule’s general acceptance under Kelly. (See id. at pp. 37-44.)

The 1996 NRC Report examined in detail the reliability of the product rule in PCR analysis. (1996 NRC Rep., supra, at pp. 116-120.) Although PCR alleles have not been researched as extensively as VNTR’s, and though PCR population databases are smaller, the NRC found that studies have shown PCR systems exhibit just as much independence as seen in VNTR’s. (Id. at pp. 35, 117.) The report cited two studies by Dr. Bruce Budowle, which found compliance with Hardy-Weinberg and linkage equilibrium principles at multiple PCR loci. (Id. at p. 117, citing Budowle, Lindsey, supra, 40 J. Forensic Sci. 45; Budowle et al., D1S80 Population Data in African Americans, Caucasians, Southeastern Hispanics, Southwestern Hispanics, and Orientals (1995) 40 J. Forensic Sci. 38 (hereafter Budowle, Baechtel).) Moreover, newer data showed that any impact of population substructure on PCR frequencies was very small. (1996 NRC Rep., supra, at pp. 35, 119.) Thus, the NRC concluded that PCR-based systems “are ready to be used along with VNTRs” (id. at p. 119) and recommended that probability calculations be made using the product rule. (Id. at pp. 38, 122.) The NRC also suggested the use of a slightly higher correction factor in PCR product rule calculations, to account for the fact that PCR population data have been less extensively studied than for VNTR’s. (Id. at p. 122.)

At the Kelly hearing, prosecution expert Charlotte Word testified she is familiar with various studies that have confirmed the independence of the PCR loci at issue in this case: DQ-alpha, polymarker and D1S80. Word knew of no published article disagreeing with the use of the product rule to calculate PCR profile frequencies, and she attested that this rule is commonly used throughout the forensic community in connection with PCR. DOJ criminalist Gary Sims gave similar testimony.

To demonstrate that a controversy exists on this issue, appellant points only to the testimony of his expert, Laurence Mueller, and an essay Mueller later published. (Mueller, The DNA Typing Controversy and NRC II in Statistics in Genetics (Halloran & Geisser edits., 1999) pp. 1-23.) Mueller acknowledges that all published studies have confirmed the independence of PCR markers; however, he claims he found “significant departures” from Hardy-Weinberg equilibrium when he pooled and reanalyzed the data from these studies. (Id. at p. 6.) However, appellant cites no peer-reviewed scientific study that supports this conclusion, and it is far from clear that Mueller’s own work was subjected to rigorous peer review. Mueller’s criticisms of the product rule contradict the great weight of published scientific opinion, and they were implicitly rejected by the 1996 NRC Report.

Dr. Mueller’s lone dissent is not sufficient to generate a controversy where the remainder of the scientific community has reached consensus on use of the product rule in PCR analysis, The Kelly test “does not demand ‘absolute unanimity of views in the scientific community .... Rather, the test is met if use of the technique is supported by a clear majority of the members of that community.’ ” (Leahy, supra, 8 Cal.4th at p. 612, quoting People v. Guerra, supra, 37 Cal.3d at p. 418, italics added by Leahy, see also People v. Axell, supra, 235 Cal.App.3d at p. 860 [“[T]he defense witnesses’ testimony on the issue of general acceptance did not undermine the validity of the trial court’s determination that forensic use of RFLP analysis is generally accepted in the relevant scientific community.”].)

Appellant complains the trial court could not have found that use of the product rule in PCR is generally accepted because the prosecution did not present expert testimony on this subject from a population geneticist. Dr. Charlotte Word, a molecular biologist, testified about application of the product rule in PCR analysis. Over defense objections as to her qualifications, the court allowed Word to testify about how the product rule works. She also testified—without objection—that the product rule is generally used throughout the forensic community in PCR testing and is not controversial in the scientific community. While a trial court’s ruling on expert qualifications is entitled to substantial deference on appeal (Kelly, supra, 17 Cal.3d at p. 39), the court here did not expressly find Word qualified to give an opinion as to the product rule’s reliability in PCR analysis, nor do we think such a ruling can be implied from the overruling of certain defense objections.

However, the court had ample evidence in addition to Word’s testimony demonstrating the general scientific acceptance of the product rule as applied to PCR. The 1996 NRC Report, which was the subject of much testimony by all experts in this case, unequivocally endorses the product rule for PCR statistical calculations. (1996 NRC Rep., supra, at pp. 116-122.) As the Supreme Court observed, regarding the NRC’s 1992 recommendation of the modified ceiling principle in RFLP analysis, “ ‘courts have recognized that “the [NRC] is a distinguished cross section of the scientific community. . . . Thus, that committee’s conclusion regarding the reliability of forensic DNA typing . . . and the proffer of a conservative method for calculating probability estimates can easily be equated with general acceptance of those methodologies in the relevant scientific community.” [Citation.]’ [Citation.]” (Venegas, supra, 18 Cal.4th at p. 89.) Though the NRC’s recommendation has changed (from use of a ceiling principle to the unmodified product rule), the respect courts afford conclusions