When "Trial Board" begins, a notice appears on the screen to say that this story is a true one based on the experiences of Joseph Wambaugh, the man who created this series. Before writing stories such as "The Blue Knight" about cops, Wambaugh himself was a police officer. This is why "Police Story" excels at showing the full range of police jobs and experiences. In this case, his own experiences with a Police Trial Board are dramatized here.
The story begins with an undercover drug buy. The bad guys are all caught and everything seems routine. However, one of the cops involved went to his superior to say that one of the policemen stole money during this sting operation! Wambaugh comes into the story as he's one of several officers sent out to investigate the case and determine what really happened.
This is a really interesting show, as it doesn't show Internal Affairs as evil jerks like they often have been shown on other shows. It also is interesting is because so many police shows of the era show police as being practically perfect in every way, but here this is clearly not the case. Well worth seeing...and one of the best episodes in the series.