Continuity mistake: Bernard puts down his sandwich in the house of the woman being blackmailed, after she tells him "no more sandwiches for you". Ten seconds later it's back in his hand, and put down again.
Law & Order (1990)
1 mistake in Blackmail - chronological order
Det. Lennie Briscoe: You know, if I didn't already know you don't have kids, I'd know you don't have kids.
Trivia: Before his transfer to the NYPD, Joe Fontana (played by Dennis Farina) worked as a detective in Chicago. Before becoming an actor, Farina served in the Chicago police department, both as a police officer and a detective. Farina also played a Chicago police officer on the short-lived 1980s TV series Crime Story.
Question: I don't remember if it was this show or another L&O, but there was an episode where a reporter was overseas at a military encampment, reporting on a war. While there, he explains the military's plans by drawing them in the sand. Shortly later, the encampment is attacked. How could the enemy figure out where the encampment was? The reporter never said where the location was at, only what the soldiers were planning.