Fresh Start - S6-E15
Continuity mistake: When Erin is in the ladies' room walking toward the door, she finds Anthony "lurking" in the hall, and Erin's eyeglasses which are hanging from her crew-neck top go from facing her right side, to her left side, then back to her right side, between shots. (00:31:55)
Continuity mistake: Franks makes a comment that there have only been 18 deaths last year in New York, but Danny on his own closed more than 30 in the season before.
Continuity mistake: When Danny/ Baez and Jamie go to arrest the medic, there are a few different shots where there is snow on the ground and then none, likewise no snow on cars and then a lot. (00:08:00)
Continuity mistake: As Danny and Jaime are at the range shooting near the middle of the episode, their targets from behind and the grouping of shots they take are really tight together. When they retrieve their targets a minute later, the grouping from the front is completely different and further apart than what was seen from behind the target.
Continuity mistake: One second Frank Reagan throws his glasses on his desk, the next after a brief cutaway, they are on his face. (00:36:10)
Continuity mistake: Henry sets down the pencil he was using on the crossword. In the next shot, as he is picking up his glass, it is in between his fingers. It shows him taking it from his hand with the other, but again in the next shot, is back on the crossword. (00:40:30)
Continuity mistake: Danny and Linda are hugging after Danny tells the boys to go pay your respects to the WWII Memorial. In the next shot they are standing apart as when he told them to go pay their respects to the memorial. (00:54:34)
Answer: It's a common cop show plot device. If the police on the show always acted in the most logical way (i.e. not alerting a suspect to their presence) the show wouldn't have the opportunity for an exciting foot chase.