We've written several posts about the Pennypack factors and how hard it can be to win a motion to strike in D. Del. The upshot is that it's often better to simply reach agreement on a curative remedy rather than spend time on full-blown motion practice.
Case in point: on Monday, Judge Burke denied a motion to strike a two-page supplemental expert declaration on a patentability issue. Applying the Pennypack factors, he concluded
that having to respond to the supplemental declaration (which, after all, relates to one discrete issue, and is only two pages long) would occasion some great prejudice to Defendants. The issue can be resolved by permitting Defendants to file a supplemental sur-rebuttal expert report on this point. That would cure the prejudice and would not disrupt the trial.
He then took the parties to task for raising this dispute in the first place:
Indeed, this was a proposed resolution that was discussed during the parties' meet and confer. The Court sees that the parties dispute which side offered that proposed resolution or whether it was ever accepted, but it does not matter. The point is that it should have been offered, it should have been accepted, and that would have been that. (Indeed, the effort Defendants spent filing and litigating this Motion is arguably greater than the effort it would have taken for them to prepare and file a short sur-rebuttal expert report in the first instance.)
Does this mean you should never bring a motion to strike? Of course not. But if there's an easy, inexpensive way to cure any prejudice caused by late disclosure, sometimes it's better to hold your nose and get it done.