This happened to me in the last year. I was defending a case involving an armed robbery (not a criminal defense, a civil defense of a customer that said they were injured by one of the robbers). The store had four surveillance cameras, numbered 1-4. They provided me with all four videos of that night and you can clearly see that none of the customers were touched by the bad guys.

Two customers were taken to the back of the store briefly but that was a dead spot where there were no cameras. So the jury had to decide whether they were credible about being shoved and choked in that blind spot for the 60 seconds they were back there.

We won the case -- hooray! Then a week later opposing counsel files a motion to vacate the decision and motion for new trial. Oh it turns out my client had TWELVE cameras, not four, and never disclosed them to either of us. We had previously had a hearing with the judge over those videos where I swore up and down there were only four cameras. The case was fucked and I looked like an asshole in front of the Judge. Fortunately o/c was willing to take a settlement and neither the Judge nor o/c thought that I was deliberately trying to deceive the court. Otherwise I could be fighting for my law license right now.

Funny thing is, those other cameras didn't show anything damaging either. They should have just given me the damn videos.