Continuity mistake: After the accident, Baez has a scar on her left cheek. However, during the raid, the scar moves to her right cheek and back to her left cheek. (00:27:12 - 00:49:32)
Character mistake: Sergeant Gormley is promoted to Lieutenant in the previous episode. In this episode he is referred to as Sergeant Gormley by Commissioner Reagan and Deputy Commissioner Garrett Moore at least twice.
Character mistake: In this episode, Garrett says that "Nom de Guere" means pen name. It means war name. Nom de Plume means pen name and Garrett is supposed to be an expert in his field.
Through the Looking Glass - S5-E19
Other mistake: Danny supposedly handcuffs an at-risk teenager. When the police officer takes her away to a cell, the girl isn't handcuffed. The handcuffs are just in her hands behind her back. (00:52:00)
Continuity mistake: During the family dinner, while everyone discusses the use of body cameras Frank is wearing his eyeglasses, but in the shots facing Linda during the conversation Frank's eyeglasses are gone. (00:21:40)
Continuity mistake: In the first two shots of the family dinner Henry is holding his fork up in his left hand, but in the third shot from behind him (facing the family) his raised left hand is empty with his fork lying across the plate, then it's back up in his hand in the fourth shot. (00:21:10)
Character mistake: Frank implies that Joe is the oldest child, but he was born in 1977 (1x22), Erin in 1975 (6x07), and Danny 1973 (2x17). Erin also claims she wasn't born yet when the murder of Henry's friend took place in 1977 but she would have been about two years old.
Continuity mistake: Near The End of the episode Frank Reagan pulls up to the house of the woman who has been scamming New Yorkers with the fake 911 charity. Immediately before he arrives she is putting suitcases in the trunk of her car. As he pulls up the suitcases in the trunk are different.
Character mistake: Throughout the episode they refer to the victim owning a "cement" company. In fact it was a concrete company. Although the terms cement and concrete often are used interchangeably, cement is actually an ingredient of concrete. Concrete is basically a mixture of aggregates and paste. The aggregates are sand and gravel or crushed stone; the paste is water and portland cement. (00:00:05 - 00:35:50)
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)
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.