Here's a scenario that can happen in a patent case: The patentee serves an opening expert report alleging infringement. Your expert responds, detailing every reason why the design documents show non-infringment. The patentee then serves a reply expert report, citing new documents that it says show infringement.
What do you do now? There are at least four answers: (1) move for leave to serve a sur-reply report to address the new docs; (2) just serve a sur-reply report, without leave, and fight the inevitable motion to strike; (3) skip the report but have the expert be prepared to discuss the new papers at deposition, and hope plaintiff asks; or (4) just plan to address the new …