Case in point: on Friday, Judge Andrews granted a motion to strike DOE theories asserted for the first time in an opening expert report. The plaintiff offered a number of excuses for disclosing the theories when it did—"it was only able to collect evidence to support its new DOE theories" after a COVID-delayed source code review, it lacked supporting evidence until a technical deposition in November 2020, and so on.
Judge Andrews not only rejected these excuses, but took it a step further—coming very close to finding that the plaintiff acted in bad faith:
No court likes to say that a party acted in bad faith. That being said, I do not understand how Plaintiff’s experienced lawyers could have thought that springing clearly new theories on a defendant in opening expert reports was in compliance with the scheduling order, the Rules, or expected standards of practice. While I do not find Plaintiff acted in bad faith, its actions approach that standard. Plaintiff’s failure to convincingly explain its choice not to timely disclose its new DOE and literal infringement theories—especially since Plaintiff has always carried the burden of proving infringement—and the prejudice to Defendant since it cannot now engage in discovery related to these new theories, taken together, justify the exclusion of the portions of the Expert Report that opine on those theories.
So again, while the Pennypack factors are lenient, they're not a panacea against exclusion—especially if there isn't a convincing reason for the delay.