Full opinion text
OPINION ARTHUR J. TARNOW, District Judge. I. Factual and Procedural Background..........................................572 II. The Dellarussiani suit......................................................574 A. Considering the offer of judgment.......................................574 B. Mootness of counts I and II in view of offer of judgment....................575 C. Reasonable attorneys’ fees..............................................576 D. Liquidated damages under Ohio’s Prompt Pay Act.........................577 III. Motion to dismiss Dellarussiani plaintiffs from O’Brien appeal ..................579 A. Mootness due to Dellarussiani judgment on counts I and II.................579 B. Defendants’ argument that mootness of the FLSA claim necessarily renders any supplemental claims moot .................................579 C. Res judicata and the Dellarussiani plaintiffs’ Prompt Pay Act claim in O’Brien....................................:.......................581 D. Res judicata and Dellarussiani plaintiffs’ common-law claims in O’Brien.....582 IV. The O’Brien suit...........................................................583 A. Decertification........................................................583 1. Standard of review.................................................584 2. The meaning of “similarly situated” ..................................584 B. The lead plaintiffs in O ’Brien............................................587 1. Spoliation.........................................................587 2. O’Brien...........................................................588 a. Rogan deposition ..............................................589 b. Deposition in the instant ease....................................590 c. Affidavit......................................................592 d. Summary Judgment............................................596 3. Prater............................................................596 a. Affidavit ¶¶ 6-9................................................596 b. Affidavit ¶¶ 10-13............ 597 c. Affidavit ¶¶ 15-16............ 599 d. Affidavit ¶ 14; Exhibits 6 and 7 601 e. Summary judgment.......... 602 4. Burden of proof.................. 602 V. Conclusion......................... 603 These appeals involve two related cases in which former employees of two McDonald’s franchises allege that their employer refused to pay the employees the wages that they were due, in violation of the Fair Labor Standards Act (“FLSA”), 29 U.S.C. § 216(b); the corresponding Ohio statute; and other Ohio law. For the reasons that follow, in the Dellarussiani appeal, we affirm the district court’s entry of judgment pursuant to the defendants’ Fed.R.Civ.P. 68 offer of judgment, except that the issue of attorney fees is remanded to the district court. Having achieved all the relief that they could hope to get on their most important claims, the Dellarussiani plaintiffs no longer have a stake in these claims in the O’Brien case. As for an Ohio Prompt Pay Act claim, which plaintiffs lost in Dellarussiani on summary judgment, and as to common-law claims pleaded in O’Brien but not in Dellarussiani, the appeal is not moot, though these claims will be barred by res judicata. Therefore, defendants’ motion to dismiss the Dellarussiani plaintiffs from the O’Brien appeal is granted in part, but denied in part as to the Prompt Pay Act and common-law claims. Though we disagree with the standard that the district court applied in deciding whether the O’Brien plaintiffs were “similarly situated” under the FLSA, we affirm the decertification. We do so, because in view of our dismissal of most of the Dellarussiani plaintiffs’ claims from the O’Brien appeal, there is only one possible opt-in plaintiff who could join the lead plaintiffs in O’Brien. But the district court correctly observed that this particular opt-in plaintiff failed to allege that she suffered from any unlawful practices. She is clearly not similarly situated to the lead plaintiffs. Nor are the Dellarussiani plaintiffs, who have only a few extant supplemental claims, similarly situated to the lead plaintiffs, given that these claims will inevitably be barred by res judicata. Therefore, we affirm the district court’s decertification of the collective action. That leaves the claims of the lead O’Brien plaintiffs. As to the lead plaintiffs, we reverse the district court’s grant of summary judgment in defendants’ favor as to the lead plaintiffs’ “off the clock” claims and vacate the grant of summary judgment as to the lead plaintiffs’ claim that their time-sheets were improperly altered. I. Factual and Procedural Background The defendants in this case are Ed Donnelly and the corporation that he and his wife own, Ed Donnelly Enterprises, Inc. O’Brien J.A. 150. Defendants bought two McDonald’s stores in Bellefontaine, Ohio in February 2002. O’Brien J.A. 155. For varying lengths of time between 2002 and 2004, plaintiffs worked in at least one of these two stores. They earned wages between $6.25 and $9.00 per hour. O’Brien Appellants’ Br. at 7. Plaintiffs allege that there were two main ways in which defendants and their managers paid plaintiffs less than what they had earned. The first practice involved requiring plaintiffs to work “off the clock,” that is, before they had punched into, or after they had punched out of, the computerized system that tracked employees’ start, end, and break times. The second manner in which plaintiffs claim they were cheated is this: plaintiffs say that defendants electronically altered the times that had previously been entered by the timekeeping system when an employee punched in or out of work. These edits, according to plaintiffs, reduced the total number of hours recorded in the employees’ payroll reports to a number less than what the employees had actually worked. In O’Brien v. Ed Donnelly Enterprises, Inc., and Ed Donnelly, plaintiffs brought the following claims: the first cause of action was for violations of the FLSA; the second, for violations of Ohio’s corresponding wage-payment law, O.R.C. § 4111; the third, for violations of Ohio’s Prompt Pay Act, O.R.C. § 4113.15(B); the fourth, for fraud; the fifth, for breach of contract; and the sixth, for promissory estoppel. The district court initially certified a class of plaintiffs under the FLSA. The ultimate class of plaintiffs (two lead plaintiffs and eight opt-in plaintiffs) moved for sanctions against defendants for spoliation of evidence. This request was denied. After discovery, the district court found that the opt-in plaintiffs were not similarly situated and decertified the class, dismissing the eight opt-in plaintiffs without prejudice. All plaintiffs but one appealed the decertification order, and this appeal is before this court. Retaining the same counsel as used in the O’Brien action, six opt-in plaintiffs refiled individual suits, which were consolidated as Dellarussiani v. Ed Donnelly Enterprises, Inc., and Ed Donnelly. Stevie LeVan, another opt-in plaintiff, did not file an individual action, but joins the O’Brien appeal. The two lead plaintiffs in O’Brien proceeded individually in that case. After striking several affidavits as inconsistent with prior deposition testimony, the district court granted summary judgment in favor of the defendants against both plaintiffs. The two O’Brien plaintiffs appealed this final judgment and several of the evidentiary decisions made by the district court. This appeal is also before this court. Each of the Dellarussiani plaintiffs filed a three-count complaint. Count I claimed violations of the FLSA; count II claimed violations of the corresponding Ohio statute; and count III alleged that defendants were required to pay liquidated damages under Ohio law, separate from any FLSA damages. Defendants made an offer of judgment pursuant to Fed.R.Civ.P. 68 with regard to counts I and II. Defendants offered to pay $6,142.20 (the full amount of claimed damages for counts I and II) plus reasonable attorney fees as determined by the district court. The offer allowed the district court to decide count III on the merits. The Dellarussiani plaintiffs rejected the offer; however, the district court found that defendants’ offer of judgment mooted counts I and II. The district court entered judgment in favor of the Dellarussiani plaintiffs in the amount of the offer on counts I and II. The district court also determined reasonable attorney fees and costs to be $6,024.94. In making this determination, the district court found that the bills submitted by the Dellarussiani plaintiffs’ counsel included time spent both on the unsuccessful O’Brien case and the successful Dellarussiani case. In addition, the bills did not properly explain what expenses were incurred in preparation solely for Dellarussiani. The district court awarded attorney fees and costs only for the work it determined was done solely for the Dellarussiani action, even though some of the evidence used in Dellarussiani was gathered during the O’Brien action. Regarding count III, the district court granted defendants’ motion for summary judgment, finding that the wages in question were in dispute. According to the district court, under Ohio Rev.Code § 4113.15(B), if wages are in dispute, an employer is not liable for liquidated damages. The Dellarussiani plaintiffs appealed the district court’s entry of judgment on counts I and II, the attorney-fees award, and the grant of summary judgment on count III. Defendants filed a motion with this court to dismiss the Dellarussiani plaintiffs from the O’Brien appeal, asserting that the Dellarussiani plaintiffs’ claims in O’Brien were mooted by the district court’s entry of judgment in the Dellarussiani plaintiffs’ favor. II. The Dellarussiani suit The six Dellarussiani plaintiffs contend that the district court erred (1) when it considered defendants’ offer of judgment, (2) when it dismissed counts I and II of their complaint for mootness in view of the offer of judgment, (3) when it refused to award any attorneys’ fees that were incurred in O’Brien while prosecuting the Dellarussiani plaintiffs’ claims, and (4) when it granted summary judgment in defendants’ favor on count III. We affirm the district court’s disposition of these issues, except as to the award of attorney fees. A. Considering the offer of judgment Plaintiffs maintain that the district court abused its discretion by even considering the offer of judgment, because Fed. R.Civ.P. 68(b) states that “[ejvidence of an unaccepted offer is not admissible except in a proceeding to determine costs.” The district court considered the offer of judgment on defendants’ Rule 12(b)(1) motion to dismiss for lack of subject-matter jurisdiction. Both the district court and the defendants explain that a district court can consider an offer of judgment to determine whether a claim is moot, in order to ascertain whether there is a justiciable case or controversy under Article III of the Constitution. In other words, an offer of judgment cannot be used to support or challenge the merits of a claim and to thereby influence the trier of fact. See Hopper v. Euclid Manor Nursing Home, 867 F.2d 291, 295 (6th Cir.1989) (“The rule contemplates that whether jury or judge tries the case the decisionmaker will be unaware of the extraneous fact that an offer of judgment has been made. This ensures that the trier of fact will not be influenced in its evaluation of the case by any knowledge of a rejected offer or the consequences thereof.”). But a Rule 68 offer can be used to show that the court lacks subject-matter jurisdiction. See Greisz v. Household Bank (III.), N.A., 176 F.3d 1012, 1015 (7th Cir.1999) (an offer of judgment that encompasses the relief claimed “eliminates a legal dispute upon which federal jurisdiction can be based,” because “[y]ou cannot persist in suing after you’ve won”); cf. Drs. Hill & Thomas Co. v. U.S., 392 F.2d 204 (6th Cir.1968) (government offered, though not pursuant to Rule 68, to give more money to tax-refund claimant than was claimed and district court correctly dismissed the claim as moot). We agree with the Seventh Circuit’s view that an offer of judgment that satisfies a plaintiffs entire demand moots the case and reject the plaintiffs’ contention that the offer of judgment could not be considered. We also note that our decision does not implicate Sandoz v. Cingular Wireless LLC, 553 F.3d 913, 922 (5th Cir.2008). That court held that a Rule 68 offer of judgment cannot moot a lead plaintiffs FLSA claim when the lead plaintiff timely moves for collective certification, because the motion relates back to the lead plaintiffs filing of the complaint. Of course, if the court eventually denies the motion, then the lead plaintiff represents only herself, and her claim is moot. Contrary to the Sandoz plaintiff, the Dellarussiani plaintiffs did not purport to bring a collective action, so we are not concerned that the Dellarussiani plaintiffs have been picked off by defendants to avoid the onslaught of a putative collective action. We disagree, however, with the Seventh Circuit’s view that a plaintiff loses outright when he refuses an offer of judgment that would satisfy his entire demand. See Greisz, 176 F.3d at 1015 (barring recovery of any damages or attorney fees when the plaintiff refused an offer of judgment for the full amount of damages plus reasonable costs and attorney fees). Instead, we believe the better approach is to enter judgment in favor of the plaintiffs in accordance with the defendants’ Rule 68 offer of judgment, as the district court did in this case, following the lead of district courts in the Second Circuit. See Greif v. Wilson, Elser, Moskowitz, Edelman & Dicker LLP, 258 F.Supp.2d 157, 160-61 (E.D.N.Y.2003); Ambalu v. Rosenblatt, 194 F.R.D. 451, 453 (E.D.N.Y.2000). B. Mootness of counts I and II in view of offer of judgment Plaintiffs maintain that the district court erred in dismissing counts I and II for mootness. In particular, plaintiffs argue that the defendants’ offer of judgment did not include attorneys’ fees and costs. True, the defendants’ offer did not offer a number certain for plaintiffs’ attorneys’ fees. But the defendants did offer to pay costs accrued and a reasonable attorneys’ fee to be determined by the court. Dellarussiani J.A. 281. Plaintiffs do not argue that they could have obtained anything more for their substantive claims in counts I and II than what the defendants offered. The only issue is whether an offer of judgment which offers to pay a reasonable attorneys’ fee as later determined by the court — but which does not offer to pay whatever sum reported by opposing counsel — moots the FLSA and corresponding Ohio claim in this case. The district court noted that offers of judgment with language similar to defendants’ offer have been deemed by other district courts sufficient to moot the claims at issue. See Ambalu, 194 F.R.D. at 452; see also Greisz, 176 F.3d at 1014 (defendant who offered judgment of “$1,200 plus reasonable costs and attorneys’ fees” in a Truth in Lending Act case was “offering [plaintiff] more than her claim was worth to her in a pecuniary sense”). Furthermore, the FLSA does not entitle a prevailing plaintiffs’ counsel to get whatever fee counsel claims. Rather, under the statute, the “court ... shall ... allow a reasonable attorney’s fee.” 29 U.S.C. § 216(b). Defendants’ offer to pay the reasonable attorneys’ fee as determined by the court is consonant with the statutory language which requires that the court “allow” the reasonable fee when it awards a judgment to a FLSA plaintiff. Plaintiffs also contend that the offer did not purport to satisfy plaintiffs’ claim for liquidated damages under Ohio Revised Code § 4113.15(B). However, the offer was only extended as to counts I and II. Dellarussiani J.A. 281. Count III, which entailed plaintiffs’ claim to liquidated damages under Ohio law, proceeded to summary judgment. See infra Part II.D. Therefore, the district did not err when it dismissed counts I and II as moot in view of the offer of judgment. C. Reasonable attorneys’ fees Plaintiffs’ counsel incurred fees of roughly $6,000 in this case and $150,000 in O’Brien. Dellarussiani J.A. 42. The district court determined that the reasonable fee to which plaintiffs’ counsel were entitled did not include the O’Brien fees. Dellarussiani J.A. 47. We review under an abuse-of-discretion standard. Wells v. New Cherokee Corp., 58 F.3d 233, 239 (6th Cir.1995). Plaintiffs contend that the Dellarussiani plaintiffs’ claims were prosecuted primarily in O’Brien. But the district court and defendants reason that the statute authorizes an award of fees only in “the action” where a plaintiff prevails. 29 U.S.C. § 216(b) (“The court in such action shall, in addition to any judgment awarded to the plaintiff or plaintiffs, allow a reasonable attorney’s fee to be paid by the defendant, and costs of the action.”) (emphasis added); Dellarussiani J.A. 44. The plaintiffs did not prevail in O’Brien, and therefore, say defendants, any fees incurred in O’Brien cannot be awarded. Such a wooden reading of the statute is unnecessary, and at a different point in the district court’s opinion, the court appears to acknowledge this. See Dellarussiani J.A. 46 (district court expressing difficulty in determining “how much time was spent on tasks in the O’Brien matter that were necessary, not redundant, and contributory to the success of the six plaintiffs” on counts I and II of Dellarussiani). The reality is that discovery concerning the Dellarussiani plaintiffs’ claims took place in O’Brien. Expenses that plaintiffs’ counsel incurred while trying to obtain collective-action certification in O’Brien should not be attributed to prosecution of the Dellarussiani plaintiffs’ particular claims, unless these expenses benefitted the Dellarussiani plaintiffs’ individual claims. For instance, fees for depositions in O’Brien that uncovered the facts surrounding the Dellarussiani plaintiffs’ claims, even if the depositions were conducted as part of the O’Brien plaintiffs’ effort to obtain collective-action certification, should not be rejected on the basis of the FLSA. Consonant with our conclusion that the statute does not bar the district court from awarding attorney fees incurred in the O’Brien suit for the Dellarussiani plaintiffs’ claims, the proper amount of attorney fees is an issue remanded to the district court. We do so notwithstanding the inadequacy and perhaps even the impropriety in the billing records that plaintiffs’ counsel had originally presented to the district court. The plaintiffs can have one more opportunity to present records that reflect fees incurred in pursuit of and which benefitted the Dellarussiani plaintiffs’ claims on which they prevailed pursuant to the Rule 68 offers that included reasonable attorney fees. Plaintiffs are advised, however, that Hensley v. Eckerhart, 461 U.S. 424, 435, 103 S.Ct. 1933, 76 L.Ed.2d 40 (1983) does not entitle them to the entirety of their fees incurred in O’Brien. As we explained in Imwalle v. Reliance Medical Products, Inc., 515 F.3d 531, 554-55 (6th Cir.2008), Hensley held that a prevailing plaintiffs lodestar amount — that is, the hours expended multiplied by the hourly billing rate — cannot be reduced for lack of overall success if some claims were successful and others were unsuccessful, when all of those claims “are based on a common core of facts or are based on related legal theories.” Imwalle, 515 F.3d at 554. Hensley does not mean that all of the fees in O’Brien can be recouped, even if arguendo the claims of all of the O’Brien plaintiffs, including those who splintered off to Dellamssiani, were based on a “common core of facts.” Addressing some of defendants’ concerns, we note that, absent a specific showing of benefit to the Dellarussiani plaintiffs, fees cannot be recovered for expenses incurred for the claims of O’Brien plaintiffs who did not file suit in Dellarussiani, nor for the claims of the lead plaintiffs in O’Brien who remained after the collective action was decertified. D. Liquidated damages under Ohio’s Prompt Pay Act Count III of the Dellarussiani complaint sought liquidated damages available under Ohio Revised Code § 4113.15(B), also known as the Prompt Pay Act or the Prompt Payment Act, which states: Where wages remain unpaid for thirty days beyond the regularly scheduled payday or, in the ease where no regularly scheduled payday is applicable, for sixty days beyond the filing by the employee of a claim or for sixty days beyond the date of the agreement, award, or other act making wages payable and no eontest[,] court order or dispute of any wage claim including the assertion of a counterclaim exists accounting for nonpayment, the employer, in addition, as liquidated damages, is liable to the employee in an amount equal to six per cent of the amount of the claim still unpaid and not in contest or disputed or two hundred dollars, whichever is greater. (Emphasis added). The district court found that disputes accounting for nonpayment of the wages claimed by plaintiffs did exist and that therefore as a matter of law, plaintiffs could not receive liquidated damages. See Dellarussiani J.A. 28. So the trial court granted the employer’s motion for summary judgment on count III. We agree. The district court correctly reasoned that Ohio law requires that a dispute accounting for nonpayment precludes the award of liquidated damages to a wage claimant. See, e.g., Jones v. Select Indus. Corp., 2006 WL 1705201, at *6 (S.D.Ohio 2006) (“where the employer disputes the wage claim, no liquidated damages are due”). Plaintiffs contend that there was no dispute in this case, because the employer never informed its employees that the employer was disputing the employees’ entitlement to certain wages. Dellarussiani Appellants’ Br. at 36. But the statute does not require such interaction between an employer and an employee. And even though the cases cited by defendants involve situations where an employer had to decide whether wages were due as a matter of policy, nothing in the statute limits a dispute accounting for nonpayment to such situations. See Fridrich v. Seuffert Construction Co., Inc., 2006 WL 562156, at *4 (Ohio Ct.App.2006) (deciding that “dispute existed as to whether Seuffert Construction’s vacation policy required the payout for unused vacation days”); Haines & Company, Inc. v. Stewart, 2001 WL 166465, at *3 (Ohio Ct.App. 2001) (holding that where parties disputed whether certain commissions were “wages” under Prompt Pay Act, a “contest” existed, meaning no liquidated damages were available). We see no reason why a factual dispute over the hours worked could not suffice as a dispute accounting for nonpayment. Next, plaintiffs suggest that the district court’s broad interpretation of what constitutes a dispute allows any recalcitrant employer to reflexively invoke the safe harbor that a dispute existed. Dellarussiani Reply Br. at 9. That, according to plaintiffs, would render as surplus the statute’s provision of liquidated damages. But there could be situations where, under the district court’s interpretation of the statute, the liquidated-damages provision could come into play. Suppose an employer had promised to pay a certain sum, and the employees agreed that this sum was their due wage. However, a clerical glitch prevented the sum from being delivered to the employees. In such a situation, the employer could not reasonably maintain that a “dispute” accounted for nonpayment. Likewise, if an employer were short on incoming cash, and consequently had to delay paying its employees, but conceded the employees’ entitlement to payment, the employer could not reasonably argue that a “dispute” accounted for nonpayment. Further, because application of the statute’s safe harbor requires that there be a contest, court order, or dispute of a wage claim accounting for nonpayment, it is proper to focus on whether the asserted dispute accounts for the nonpayment. Thus, it is not the case that any recalcitrant employer can simply declare that there is a dispute and then retroactively insulate its actions. Concerning Dellarussiani, the defendants disputed that they owed anything more than what they paid their employees according to the employer’s own payroll records. Contrary to plaintiffs’ argument, the offer of judgment does not undermine the existence of a dispute accounting for nonpayment, because the Rule 68 offer did not concede liability; it was a procedural tool to encourage the quick resolution of litigation. Dellarussiani J.A. 281-82. Plaintiffs suggest that a jury decide whether a dispute existed. Dellarussiani Appellants’ Br. at 36. However, plaintiffs have failed to raise a genuine issue of material fact, as required under Rule 56, as to whether defendants’ disputes with the plaintiffs count as “dispute[s]” under the statute. The district court examined the facts surrounding each of the plaintiffs’ claims and concluded that a dispute accounting for nonpayment did indeed exist. Dellarussiani J.A. 32-38. The district court framed its inquiry as one determining whether the evidence demonstrated “a reasonable basis upon which Defendants disputed” the plaintiffs’ claims. Although asking whether the defendant has a “reasonable basis” for disputing the claims does not flow directly from O.R.C. § 4113.15(B), the district court’s “reasonable basis” gloss aided its consideration of whether there was a genuine issue regarding whether there was a contest or dispute “accounting for nonpayment.” Plaintiffs have not shown that the district court erred in concluding as a matter of law that there was no genuine issue of material fact whether there was a contest or dispute accounting for nonpayment. Even if plaintiffs may have provided evidence creating an issue of fact as to whether the underlying FLSA and wage-payment violations occurred, that evidence, even when viewed most favorably towards plaintiffs, does not suggest that there was no dispute accounting for nonpayment. Rather, the evidence, even when viewed in the required light, establishes that a contest or dispute regarding defendant’s liability for further wages accounted for its nonpayment. Alternatively, if plaintiffs had evidence that the wages were withheld even though defendants conceded or reasonably had to concede that the wages were due, such evidence — like evidence about clerical glitches or cash-flow problems — could create a triable issue of fact on the Prompt Pay Act claim. But in our case, the plaintiffs have no such evidence: the reason that the lawsuit has continued is that defendants do not concede that the wages claimed by plaintiffs are due. Therefore, the district correctly granted summary judgment in defendants’ favor on count III. III. Motion to dismiss Dellarussiani plaintiffs from O’Brien appeal Arguing that we lack subject-matter jurisdiction due to mootness, defendants move to dismiss from the O’Brien appeal the plaintiffs who splintered off from the O’Brien case following decertification so that they could file individual claims in Dellarussiani. The motion is granted in part and denied in part. We explain why in four parts: (A) mootness due to Dellarussiani judgment on counts I and II; (B) defendants’ argument that mootness of the FLSA claim necessarily renders any supplemental claims moot; (C) the hurdle of res judicata for the Dellarussiani plaintiffs’ Prompt Pay Act claim in O’Brien; (D) and the res judicata bar against the common-law claims that Dellarussiani plaintiffs have in O’Brien. A. Mootness due to Dellarussiani judgment on counts I and II Because we affirm the district court’s entry of judgment in the Dellarussiani plaintiffs’ favor on counts I and II, any of the plaintiffs’ corresponding claims in O’Brien — claims that they hope to maintain if the district court’s decertification is reversed on appeal — -are now moot. There is no longer a live controversy as to the FLSA and the corresponding Ohio wage-payment claim, Gottfried v. Med. Planning Servs., Inc., 280 F.3d 684, 691 (6th Cir.2002), because there is no other relief that plaintiffs could obtain on those claims in O’Brien, given our overall affirmance of the district court’s rulings in Dellarussiani and our remand of the attorney-fees issue in Dellarussiani. B. Defendants’ argument that mootness of the FLSA claim necessarily renders any supplemental claims moot Defendants suggest that our inquiry stops here, because the only claim in O’Brien that is statutorily capable of proceeding collectively is the FLSA claim. Appellees’ Reply in Supp. of Mot. to Dismiss at 3. Given that the FLSA claim that the Dellarussiani plaintiffs had in O’Brien has been mooted by the judgment entered in Dellarussiani pursuant to the Rule 68 offer, the collective-action device is unavailable, according to defendants’ theory, for the Dellamssiani plaintiffs’ supplemental claims that remain in O’Brien. Defendants maintain that because the Dellarussiani plaintiffs’ appeal in O’Brien seeks reinstatement into a collective action, the unavailability of this vehicle means that their appeal is moot. We reject this argument. In general, as we discuss in Part IV.A, if a FLSA lead plaintiff also brings supplemental state claims and then seeks certification as a collective action, a district court evaluates whether the opt-in plaintiffs are “similarly situated” under 29 U.S.C. § 216(b). If the opt-in plaintiffs are similarly situated to the lead plaintiffs, it does not make sense to suggest, as defendants seem to, that only the FLSA claims may proceed collectively, while the supplemental claims would have to proceed individually or would be required to run in parallel to the collective action only by satisfying the more stringent requirements of Fed.R.Civ.P. 23. See, e.g., Molina v. First Line Solutions, 566 F.Supp.2d 770, 789-90 (N.D.Ill.2007) (declining to certify a parallel Fed.R.Civ.P. 23(b)(3) class of supplemental claims alongside a FLSA collective action, but allowing any opt-in plaintiffs to pursue supplemental claims as part of a collective action). To disjoin FLSA and supplemental claims in the manner proposed by defendants would defeat the purpose of supplemental jurisdiction, which is to facilitate the resolution of claims that are so closely related to claims for which federal jurisdiction originally lies that the supplemental claims are part of the same case or controversy as the claim independently invoking federal jurisdiction. See 13D Wright, Miller, Cooper, & Freer, Federal Practice and Procedure § 3657 at 317 n. 4 (3d ed. 2008). Notwithstanding the lack of express statutory authority in the FLSA for collective certification of non-FLSA claims, supplemental claims by definition are treated as part of the same controversy animated by a particular employee’s FLSA claim. See 28 U.S.C. § 1367(a). So far, we have explained that an opt-in employee with FLSA and supplemental claims can have both of those claims certified as part of a collective action where a lead plaintiff has FLSA and supplemental claims. That is the background for the situation we face, where a lead plaintiff has FLSA and supplemental claims, but an opt-in employee only has supplemental claims. In Exxon Mobil Corp. v. Allapattah Services, Justice Ginsburg explained the Court’s unanimous understanding that 28 U.S.C. § 1367(a) confers supplemental jurisdiction in cases where one plaintiff has a claim invoking federal-question jurisdiction, 28 U.S.C. § 1331, but other plaintiffs only have state claims. 545 U.S. 546, 587-88, 125 S.Ct. 2611, 162 L.Ed.2d 502 (2005) (Ginsburg, J., dissenting); see id. at 559, 125 S.Ct. 2611 (majority opinion) (“If the court has original jurisdiction over a single claim in the complaint, it has original jurisdiction over a ‘civil action’ within the meaning of § 1367(a), even if the civil action over which it has jurisdiction comprises fewer claims than were included in the complaint. Once the court determines it has original jurisdiction over the civil action, it can turn to the question whether it has a constitutional and statutory basis for exercising supplemental jurisdiction over the other claims in the action.”); see also Lindsay v. Gov’t Employees Ins. Co., 448 F.3d 416, 423 (D.C.Cir.2006) (analyzing Allapattah and holding in a case involving FLSA and state-law claims that “so long as the district court has original jurisdiction over a single claim, it may exercise supplemental jurisdiction over any additional claim that forms part of the same Article III case or controversy”). Under Allapattah, § 1367(a)’s requirement that the section only apply “in any civil action of which the district courts have original jurisdiction” is clearly satisfied when a single claim invoking federal-question jurisdiction exists. Thus, an inquiry whether supplemental jurisdiction exists over state-law claims need only examine whether the state claims are so closely related to the federal claim that the state claims form part of the same Article III case or controversy as the federal claim. Therefore, as long as someone in a collective action has a FLSA claim, employees who are similarly situated can be part of the collective action, even if .the other employees only have supplemental claims. Accordingly, if for some reason, a particular employee or group of employees did not have viable FLSA claims, due to mootness or claim preclusion, for instance, but had extant supplemental claims, a court would examine whether these employees were still similarly situated to the lead plaintiffs, which they may or may not be. The short of our discussion is that we have jurisdiction to consider whether the Dellarussiani plaintiffs, who have only supplemental claims that are still alive, could still be part of the collective action, were we to remand the ease for recertification. Even though the Dellarussiani plaintiffs’ FLSA claim in O’Brien is now moot due to the Dellarussiani judgment, the FLSA only requires an analysis of whether these plaintiffs are similarly situated to the lead plaintiffs whom they would join upon a putative remand for recertification of the collective action. That similarly-situated analysis is not mooted by the lack of a FLSA claim on the part of the employees who seek to opt into the collective action. C. Res judicata and the ■ Dellarussiani plaintiffs’ Prompt Pay Act claim in O’Brien We turn therefore to the other supplemental claims. With respect to the plaintiffs’ third claim in O’Brien for liquidated damages under Ohio’s Prompt Pay Act, O.R.C. § 4113.15(B): In Dellarussiani, this claim died on summary judgment, and above, we explain why we affirm the district court’s disposition of count III. But the Dellarussiani plaintiffs still have a Prompt Pay Act claim in O’Brien. Mootness typically would not bar the Dellarussiani plaintiffs’ § 4113.15(B) claim in O’Brien, in view of their loss at summary judgment on an identical claim in other litigation. Ordinarily, when a claim has already been resolved in a prior suit, mootness is invoked as a bar to subject-matter jurisdiction when “full relief’ has been accorded by the prior tribunal. See, e.g., Davis v. Sun Oil Co., 148 F.3d 606, 611 n. 4 (6th Cir.1998). Indeed, this is the case for counts I and II of Dellarussiani: plaintiffs have already won on these claims in Dellarussiani, and there is nothing more for them to win on a putative remand in O’Brien, particularly since we are remanding to the Dellarussiani district court the issue of what attorney fees can be recouped. That is why the Dellarussiani plaintiffs’ are dismissed from the O’Brien appeal as to their FLSA and O.R.C. § 4111 claims. But with regard to the Prompt Pay Act claim for liquidated damages, the Dellarussiani plaintiffs in O’Brien are not, strictly speaking, barred by mootness but by claim preclusion. This fine distinction is worth discussing, because if mootness were to apply when a losing party received an adverse ruling but persisted in seeking relief in a subsequent suit, a federal court sitting in that subsequent suit would be required to sua sponte inquire into its own subject-matter jurisdiction over the previously losing party’s claim. In other words, whether res judicata applied would be probative of whether the subsequent claim was moot and whether the claim was justiciable. But Fed.R.Civ.P. 8(c) clearly frames res judicata as an affirmative defense, which means that it can be waived and that it does not go to subject-matter jurisdiction. See O’Connor v. Pierson, 426 F.3d 187, 194 (2d Cir.2005). Therefore, losing a claim on summary judgment in a previous suit does not moot such a claim in a subsequent lawsuit. Rather, the subsequent claim is barred under the doctrine of claim preclusion. See Ohio Nat. Life Ins. Co. v. U.S., 922 F.2d 320, 325 (6th Cir.1990). Under Sixth Circuit Rule 27(d)(1), “[mjotions to dismiss ordinarily may not be filed on grounds other than lack of jurisdiction.” This rule favors denying the defendants’ motion to dismiss as to the Dellarussiani plaintiffs’ Prompt Pay Act claim in O’Brien, because claim preclusion, not mootness, is the obstacle that plaintiffs face on this claim. The individual Dellarussiani plaintiffs could then conceivably be recertified into a collective action along with the lead plaintiffs in O’Brien, given our conclusion, which we discuss later in Part IV.A.2, that the district court applied the wrong standard in decertifying the collective action in O’Brien. However, on remand, the defendants would surely raise res judicata and ask the district court to dismiss the extant Dellarussiani plaintiffs’ claim once and for all. Res judicata in this instance is an “insurmountable hurdle” that has mootness-like effects. See Myer v. Americo Life, Inc., 469 F.3d 731, 733 (8th Cir.2006). Rather than grant the defendants’ motion to dismiss the Dellarussiani plaintiffs’ appeal in O’Brien as to their Prompt Pay Act claim, we instead choose to avoid transgressing the boundary between mootness and claim preclusion. The motion is denied as to the claim for § 4113.15(B) liquidated damages, but we find that under § 216(b) of the FLSA, the Dellarussiani plaintiffs are not “similarly situated” to the lead plaintiffs in O’Brien, given the inevitable preclusion of both the Prompt Pay Act claims and the common-law claims, as discussed next in Part III.D. Therefore, on the merits, we affirm the district court’s decertification of these plaintiffs’ Prompt Pay Act claim. Thus, the Dellarussiani plaintiffs are unable to rejoin the collective action. Technically, they could attempt to file individual actions, as we are affirming the district court’s decertification and dismissal without prejudice of their claim. But such suits would be nipped in the bud by the affirmative defense of claim preclusion. D. Res judicata and Dellarussiani plaintiffs’ common-law claims in O’Brien Finally, we must consider whether the Dellarussiani plaintiffs’ appeal from the decertification order in O’Brien is moot as to common law claims pleaded in O’Brien. Because the FLSA and common-law claims appear to be based on the same alleged conduct, we are skeptical that the district court would afford any more relief upon a putative remand on the common-law claims in O’Brien than what the plaintiffs already received on counts I and II pursuant to the offer of judgment in Dellarussiani. Nevertheless, we cannot say as a matter of law how the disposition of a FLSA claim affects the common-law claims. That would require an analysis of the elements of and remedies offered by the common-law claims compared to the FLSA claim. It is possible that a federal claim could be moot while a supplemental claim based on the same conduct might not be. The doctrine that would definitively bar the Dellarussiani plaintiffs from pursuing their common-law claims in O’Brien upon a putative remand is claim preclusion, not mootness. Therefore, for the reasons discussed in the previous section, we have subject-matter jurisdiction over the Dellarussiani plaintiffs’ appeal as to the common-law claims, and the motion to dismiss is accordingly denied with respect to these claims. The plaintiffs pled for common-law relief in O’Brien, but not in Dellarussiani. See O’Brien J.A. 11-14; Dellarussiani J.A. 4-6. Because the district court dismissed the Dellarussiani plaintiffs from O’Brien without prejudice, the Dellarussiani plaintiffs could have brought the common-law claims in Dellarussiani. But they did not. Therefore, they will inevitably be barred by res judicata. We affirm the decertification in O’Brien as to the Dellarussiani plaintiffs: they are not similarly situated under the FLSA to the lead plaintiffs, because they will not have any claims grounded in the actionable conduct. They have nothing left to litigate in O’Brien, as all of their claims in O’Brien are moot or will be claim-precluded. IV. The O’Brien suit Therefore, only the two lead O’Brien plaintiffs and Stevie LeVan are now parties to the appeal from the O’Brien district court’s decertification order. After we discuss why the district court’s application of the “similarly situated” language from the FLSA was partly in error, we explain why the district court’s decertification of the collective action will be affirmed. We then discuss the district court’s evidentiary and summary-judgment rulings concerning the two lead O’Brien plaintiffs. A. Decertification The Fair Labor Standards Act provides a private cause of action against an employer “by any one or more employees for and in behalf of himself or themselves and other employees similarly situated.” 29 U.S.C. § 216(b) (emphasis added). Unlike class actions under Fed.R.Civ.P. 23, collective actions under FLSA require putative class members to opt into the class. See 29 U.S.C. § 216(b) (“No employee shall be a. party plaintiff to any such action unless he gives his consent in writing to become such a party and such consent is filed in the court in which such action is brought.”). These opt-in employees are party plaintiffs, unlike absent class members in a Rule 23 class action. See 7B Wright, Miller, & Kane, Federal Practice and Procedure § 1807 at 474 n. 13 (3d ed.2005). The district court followed a two-stage certification process, as many courts do, to determine whether the opt-in plaintiffs and lead plaintiffs were similarly situated. See id. § 1807 at 487 n. 48. After the initial conditional certification of the class, the parties entered into discovery. At the second stage, the district court reviewed the evidence produced during discovery and decertified the class for two main reasons. First, the district court stated that each claim presented by each plaintiff would require an extensive individualized analysis to determine whether a FLSA violation had occurred, frustrating the “collective consideration of common questions of fact and law.” O’Brien J.A. 72. Second, the alleged violations were not based on a broadly applied, common scheme, nor were the violations widespread even among the plaintiffs, who constituted only a small fraction of the total number of potential collective-action members. See J.A. 69. Specifically, out of the 426 potential collective-action members, the district court noted that evidence produced through discovery revealed that only five of the ten plaintiffs alleged that their time-sheets were altered, only five alleged that they were required to work off the clock, and three plaintiffs failed to allege that they suffered from either practice. Id. 1. Standard, of review The Sixth Circuit has not previously announced its standard for reviewing a district court’s certification rulings in the FLSA context. But the Eleventh Circuit reviews collective-action-certifieation decisions for abuse of discretion, and even the plaintiffs suggest that the court apply this deferential standard. See Anderson v. Cagle’s, Inc., 488 F.3d 945, 953-54 (11th Cir.2007). We adopt this standard. 2. The meaning of “similarly situated” The Fair Labor Standards Act does not define “similarly situated,” and neither has this court. However, district courts have based their final-certification decisions on a variety of factors, including the “factual and employment settings of the individual[ ] plaintiffs, the different defenses to which the plaintiffs may be subject on an individual basis, [and] the degree of fairness and procedural impact of certifying the action as a collective action.” See 7B Wright, Miller, & Kane, supra, § 1807 n. 65 at 497; Anderson, supra, 488 F.3d at 953. The lead plaintiffs bear the burden of showing that the opt-in plaintiffs are similarly situated to the lead plaintiffs. See 7B Wright, Miller, and Kane, supra, § 1807 at 476 n. 21. Showing a “unified policy” of violations is not required, though. See Grayson v. K Mart Corp., 79 F.3d 1086, 1095 (11th Cir.1996) (suit alleging age discrimination under Age Discrimination in Employment Act (ADEA), 29 U.S.C. §§ 621-34, which incorporates by reference the enforcement provisions of the FLSA). But see Mooney v. Aramco Sews. Co., 54 F.3d 1207, 1214 n. 8 (5th Cir.1995) (for conditional certification so that notice to putative class members could be sent, court required that plaintiffs allege that they were victims of a single decision, policy, or plan infected by discrimination), overruled on other grounds by Desert Palace, Inc., v. Costa, 539 U.S. 90, 123 S.Ct. 2148, 156 L.Ed.2d 84 (2003); Thiessen v. Gen. Elec. Capital Corp., 267 F.3d 1095, 1105 (10th Cir.2001) (same). Plaintiffs argue that they did indeed allege two common ways by which the employer violated the FLSA, namely, (1) that the defendant made employees work off the clock, and (2) that the employer or its agents improperly edited employees’ time punches after the fact, thus cutting the hours for which plaintiffs were paid. Both the district court and the defendant note that to determine whether a particular violation of the FLSA took place in this case requires an individualized analysis that examines the facts of each alleged violation. For this reason, the district court decertified, determining that individualized issues predominated. But such a collection of individualized analyses is required of the district court. Under the FLSA, opt-in plaintiffs only need to be “similarly situated.” While Congress could have imported the more stringent criteria for class certification under Fed.R.Civ.P. 23, it has not done so in the FLSA. See Grayson, 79 F.3d at 1096 (section 216(b)’s “similarly situated” requirement is less stringent than Rule 20(a) requirement that claims “arise out of the same action or occurrence” for joinder to be proper, or even Rule 23(b)(3)’s requirement that common questions predominate for a 23(b)(3) class to be certified). But see Shushan v. Univ. of Colo. at Boulder, 132 F.R.D. 263, 266-67 (D.Colo.1990) (applying Rule 23 to collective actions under 216(b) for purpose of effective management of litigation). The district court implicitly and improperly applied a Rule 23-type analysis when it reasoned that the plaintiffs were not similarly situated because individualized questions predominated. See O’Brien J.A. 70. This is a more stringent standard than is statutorily required. Granted, it is clear that plaintiffs are similarly situated when they suffer from a single, FLSA — -violating policy, and when proof of that policy or of conduct in conformity with that policy proves a violation as to all the plaintiffs. In the instant case, proof of a violation as to one particular plaintiff does not prove that the defendant violated any other plaintiffs rights under the FLSA. Nevertheless, the plaintiffs are “similarly situated” according to § 216(b). Furthermore, it is possible that representative testimony from a subset of plaintiffs could be used to facilitate the presentation of proof of FLSA violations, when such proof would ordinarily be individualized. See Morgan v. Family Dollar Stores, Inc., 551 F.3d 1233, 1263-65, 1279-80 (11th Cir.2008) (as amended) (determining that although proof of exemption from FLSA’s overtime-pay requirements might appear to be individualized, certain plaintiffs’ representative testimony could be used to show exemption’s inapplicability, as all plaintiffs in collective action were similarly situated), petition for cert. filed, 77 U.S.L.W. 3596 (U.S. Apr. 15, 2009) (No. 08-1287). We do not purport to create comprehensive criteria for informing the similarly-situated analysis. But in this case, the plaintiffs were similarly situated, because their claims were unified by common theories of defendants’ statutory violations, even if the proofs of these theories are inevitably individualized and distinct. The claims were unified so, because plaintiffs articulated two common means by which they were allegedly cheated: forcing employees to work off the clock and improperly editing time-sheets. We do not mean to require that all collective actions under § 216(b) be unified by common theories of defendants’ statutory violations; however, this is one situation where a group of employees is similarly situated. Plaintiffs offer their own interpretation of what “similarly situated” means. Instead of arguing that Rule 23(b)(3) predominance should not be a criterion for § 216(b) collection actions, plaintiffs say that putative collective-action members whose “causes of action under the FLSA accrued at about the time and place in the approximate manner of the named plaintiff would be similarly situated” to the lead plaintiffs. See O’Brien Appellants’ Br. at 20 (citing Pritchard v. Dent Wizard Intern. Corp., 210 F.R.D. 591, 595 (S.D.Ohio 2002)). Defendants explain that those cases cited by plaintiffs arise in situations where a court has to decide whether a certain class of employees is exempt from the FLSA’s overtime-pay requirements. Those cases, argue defendants, lend themselves to collective adjudication because common questions predominate. For instance, a court can easily decide whether all the dent-removal technicians (as in Pritchard) are exempt from overtime-pay requirements, without having to examine the specific factual situation of each dent-removal technician. While we agree with plaintiffs that “about the time and place in the approximate manner” is a starting point for understanding what “similarly situated” means, such an interpretation can result in a standard that is more demanding than what the statute requires, unless one excludes Rule 23 predominance from being an implicit requirement for § 216(b) collective actions. And protecting § 216(b) in this way is what we have outlined above. We do not suggest that aspects of Rule 23 could never be applied to a FLSA collective action. Rather, applying the criterion of predominance undermines the remedial purpose of the collective action device. As for the argument that the alleged unlawful practices — making employees work off the clock and altering the time-sheets — were not alleged by all of the plaintiffs, this argument ultimately requires us to affirm the decertification. Stevie LeVan is the only opt-in plaintiff who could possibly benefit from the recertification of the collective action. Unlike the Dellarussiani plaintiffs, LeVan had opted into O’Brien but did not pursue her claim in Dellarussiani. As the district court observed, LeVan is clearly not similarly situated to the lead plaintiffs, because she failed to allege that she suffered from either unlawful practice. O’Brien J.A. 69 (district-court opinion), 289 (LeVan Dep. at 33). And as we explained in Part II, the Dellarussiani plaintiffs cannot be recertified because some of their claims are moot and the others will be claim-precluded, leaving them without any claims to pursue and necessarily excluding them from being “similarly situated” under § 216(b). In general, though, a district court should examine whether partial decertification is possible, when faced with the situation where a subset of the plaintiffs fail to allege violations of the FLSA. The option of partial certification is important to consider, because it counters the argument that a collective action must be totally decertified if some members are not similarly situated to the others. In general, plaintiffs who are not similarly situated — -for instance, plaintiffs who did not allege suffering under either unlawful practice — could be dismissed while keeping intact a partial class. Plaintiffs who do present evidence that they are similarly situated to the lead plaintiffs should not be barred from the opportunity to be part of a FLSA collective action, because the collective action serves an important remedial purpose. Through it, a plaintiff who has suffered only small monetary harm can join a larger pool of similarly situated plaintiffs. See Hoffmann-La Roche, Inc., v. Sperling, 493 U.S. 165, 170, 110 S.Ct. 482, 107 L.Ed.2d 480 (1989). That pool can attract effective counsel who knows that if the plaintiffs prevail, counsel is entitled to a statutorily required reasonable fee as determined by the court. In the age-discrimination context, which also requires that opt-in plaintiffs be similarly situated for certification of a collective action, “Congress has stated its policy that ADEA plaintiffs should have the opportunity to proceed collectively.” See Gray-son, 79 F.3d at 1096. As some district courts have noted, “imposing any additional restrictions from Rule 23 would be contrary to the broad remedial goals” of the FLSA and its sister statutes — such as the Equal Pay Act, 29 U.S.C. § 206(d), and the ADEA, 29 U.S.C. § 626(b) — which incorporate the same statutory language concerning collective actions. See 7B Wright, Miller, and Kane, supra, § 1807 at 481 n. 25, at 468-69 nn. 2-3. A final word on the parties’ less persuasive points. Defendants note that some of the plaintiffs were managers and therefore could not be “similarly situated.” This is not a compelling argument, because managers could also have been cheated by defendants. Also, in their reply brief, plaintiffs mischaracterize the reasoning of the district court, implying that the district court decertified the class because plaintiffs alleged two ways, instead of one way, in which the plaintiffs suffered violations. As discussed, the district court decertified because it did not see how plaintiffs’ claims, even if based on two theories of how the FLSA violations were committed, could be adjudicated but in an individualized manner. B. The lead plaintiffs in O’Brien Having affirmed the district court’s decertification of the collective action, we turn to the claims of the lead plaintiffs in O’Brien. The district court denied their motion for sanctions due to spoliation, granted defendants’ motions to strike plaintiffs’ affidavits, and in the end, granted defendants’ motion for summary judgment. We conclude that spoliation may have taken place; therefore, this issue is remanded for the district court’s consideration. As for the district court’s other evidentiary rulings, the affidavits should not have been stricken. Apart from any consideration of the effect of possible spoliation sanctions on the merits of the lead plaintiffs’ claims, we disagree with the district court in part and reverse as to the lead plaintiffs’ off-the-clock claims. We vacate the district court’s entry of summary judgment on the lead plaintiffs’ time-sheet — alteration claims, so that the district court may revisit this disposition once it decides the spoliation issue. 1. Spoliation In a motion for discovery sanctions, plaintiffs alleged that the defendants intentionally lost or destroyed some of the Time Punch Change Approval (TPCA) Reports. O’Brien J.A. 55. In addition to seeking monetary sanctions, the employees wanted the district court to infer that the missing reports would have been adverse to the employer. Id. at 4. These TPCA reports were printed by defendants’ computer system at the end of each day, but the computer system itself only held the past 72 days in backup. O’Brien J.A. 161-62. Plaintiffs maintain that these reports are the only records that would reveal improper changes made by defendant to the time-sheets punched by the employees. See O’Brien J.A. 178-79. Although a district court’s discovery rulings are reviewed for abuse of discretion, see U.S. v. Guy, 978 F.2d 934, 938-39 (6th Cir.1992), we reverse the district court and remand for its consideration whether it was reasonably foreseeable that the missing reports would be needed in future litigation. The magistrate judge’s opinion, adopted by the district court, reasons that destruction or loss of evidence before notice of the O’Brien lawsuit is not a basis for sanctions. O’Brien J.A. 60. That is true, but the issue here concerns when the defendant was or should have been on notice that litigation requiring the missing reports as evidence might ensue. See John B. v. Goetz, 531 F.3d 448, 459 (6th Cir.2008) (duty to preserve evidence is triggered when a “party has notice that the evidence is relevant to litigation or ... should have known that the evidence may be relevant to future litigation”). The magistrate judge appears to assume that the defendant was on notice only when the O’Brien lawsuit was filed. However, the district court should consider whether the defendants should have been on notice earlier than the date of the filing of the O’Brien suit. As the district court has not yet considered whether the employer was on notice of its duty to preserve evidence before the O’Brien lawsuit, we do not conclude in the first instance that spoliation did take place. Rather, the district court can consider facts which could suggest that the employer should have anticipated that the missing records needed to be preserved. For instance, plaintiffs assert that within four to six weeks after buying the McDonald’s stores, defendant Donnelly learned that the prior owners had been sued by a former employee who claimed she had not been paid wages due her. See O’Brien Reply Br. at 7. Plaintiffs also maintain that Donnelly knew that one of his managers was changing employees’ time records by inserting breaks and that one of the managers was making employees work off the clock. See O’Brien Reply Br. at 7, 9-10. If the district court concludes that spoliation did take place, the district court can consider, under its inherent authority, whether it was negligence or bad faith that motivated the defendants and relatedly, what sanction, if any, should be imposed. Adkins v. Wolever, 554 F.3d 650, 653 (6th Cir.2009) (en banc). Plaintiffs also argue that the defendants were under a duty to preserve for longer than 72 days the electronic versions of the TPCA reports. O’Brien Appellants’ Br. at 29. But plaintiffs provide no authority for that proposition. What matters is whether the employer produces the reports in discovery, in either hard copy or electronic form. Defendants also maintain that they did in fact produce payroll records which show the hours worked. O’Brien Resp. Br. at 27. However, the payroll records would not show whether edits were made by defendants to employees’ time-sheets. The TPCA reports are therefore relevant to one of plaintiffs’ theories of how the alleged FLSA violations happened. Defendants may argue that any edits were made for good reason, see id., but the question of whether the edits were proper is separate from defendants’ obligation to produce relevant, non-privileged discovery materials. Finally, defendants argue that of the missing reports, all but two pertain to the time period before the lawsuit was filed. See O’Brien Resp. Br. at 26. But as stated above, the district court should consider whether the defendant had a duty to pres