1. When he was arrested for murder
The last thing SSA Derek Morgan expected when he flew home to Chicago for his mother's birthday was to be arrested. After a child he had been seen with earlier in the day was murdered, the Chicago detective on the case was quick to arrest Morgan. With the help of the rest of the team—particularly Garcia—Morgan was able to exonerate himself and expose the real killer: Carl Buford.
"Profiler, Profiled" (Season 2, Episode 12)