JAMES P. O'HARA, Magistrate Judge.
This is a class action brought by the former and current employees of defendants' retail stores. Plaintiffs allege that defendants breached the terms of their compensation plans and violated the Kansas Wage Payment Act by underpaying commissions to thousands of employees as a result of systematic flaws in defendants' computer systems. The case is again before the undersigned U.S. Magistrate Judge, James P. O'Hara, on disputes over expert discovery. Plaintiffs have moved the court to permit them to produce a second round of supplemental reports from their experts (doc. 432). Plaintiffs have also moved to strike a supplemental report of defendants' expert that was produced on March 11, 2013 (doc. 439). Although the court concludes that the supplemental expert reports of both sides' experts contain revisions that cannot be deemed proper supplementation under Fed.R.Civ.P. 26(e), the court will nonetheless permit them, in large part, to be served under Fed.R.Civ.P. 37(c). Accordingly, plaintiffs' motion for leave to supplement expert reports is granted and plaintiffs' motion to strike the report of defendants' expert is granted in part and denied in part.
The parties exchanged the initial reports of their experts on October 15, 2012. Plaintiffs served a report authored by both Barry Ezell and Nile Nickel of Balance Engines, LLC, and a separate report of Margaret H. Dunham. Defendants served the report of Janet R. Thornton. On December 12, 2012, plaintiffs served timely supplemental expert reports of both Balance Engines and Dunham. Defendants, upon the court's order,  served a supplemental expert report of Thornton on December 20, 2012. The parties exchanged rebuttal expert reports on February 14, 2013. Expert depositions followed. Plaintiffs deposed Thornton on February 28, 2013. Defendants deposed Dunham on March 1, 2013, Nickel on March 5, 2013, and Ezell on March 6, 2013. During the depositions, each expert testified that his or her calculations could be refined in ways that would make his or her conclusions more accurate. At the pretrial conference held on March 7, 2013, plaintiffs informed the court of their intention to file supplemental expert reports to correct inaccuracies in expert calculations. Defendants objected to the supplementation, and the court directed plaintiffs to file a motion seeking leave to supplement.
A. Plaintiffs' Second Supplemental Expert Reports
On March 11, 2013, plaintiffs filed their motion for leave to produce supplemental reports of their experts. Plaintiffs represent that their experts have "discovered information about their calculations that lead them to believe that making certain revisions to their code will result in more accurate commissions calculations for the class." Plaintiffs filed their proposed second supplemental expert reports on April 17, 2013. Plaintiffs assert that the revisions therein do not change their experts' "overall methodology."
Defendants contend that plaintiffs' proposed modifications "necessarily require a change in their experts' previous methodology." Citing an affidavit by their expert, Thornton, defendants argue that the proposed revisions would alter five of the six stages of Balance Engines's methodology. Thus, rather than supplement previous expert reports, plaintiffs would be "wholly revis[ing] them." Defendants also argue that they would be prejudiced by the late supplementations because March 25, 2013, was the deadline for dispositive and Daubert motions, and because they have already spent time and money analyzing plaintiffs' past expert reports, and preparing for and conducting the depositions of plaintiffs' experts.
B. Defendants' Second Supplemental Expert Report
On March 11, 2013, defendants served a second supplemental report of Thornton without requesting or obtaining the court's leave. Thornton's second supplemental report purports to address issues raised by plaintiffs' counsel during Thornton's deposition, admissions during the depositions of plaintiffs' experts, and the rebuttal reports of plaintiffs' experts. According to defendants, Thornton's report concludes that her underlying methodology and conclusions were sound, but makes discrete updates to her programming code.
On March 18, 2013, plaintiffs moved to strike Thornton's second supplemental report. Based on plaintiffs' motion to strike, defendants agreed to withdraw twenty-eight paragraphs of Thornton's report. Plaintiffs contend, however, that fifteen additional paragraphs contain improper sur-rebuttal to the rebuttal reports of plaintiffs' experts and must be stricken. Plaintiffs state that they do not object to the portions of Thornton's report correcting inaccurate calculations, so long as plaintiffs are permitted to serve revised expert reports doing the same.
Fed. R. Civ. P. 26 governs the disclosure of expert testimony. It provides, in relevant part, that an expert must submit a report that contains "a complete statement of all opinions the witness will express and the basis and reasons for them." Courts may set a time by which the parties must submit their experts' reports. A party bears a continuing obligation to supplement expert reports if the party later learns the information initially provided is incomplete or incorrect. When the expert disclosure rules are violated, Fed.R.Civ.P. 37(c) mandates that the information or witness not fully disclosed is barred, unless the failure to disclose was "substantially justified or harmless."
A. Do the Supplemental Reports Violate Rule 26?
The scheduling order set October 15, 2012, as the deadline for filing expert reports and December 12, 2012 (i.e., forty days before the discovery deadline), as the deadline for supplementing expert reports. The latest round of ...