Continuity mistake: Danny and the ESU enter the warehouse basement to find Bobby, and when they start to return fire, the first guy they shoot knocks over the white plastic lawn chair (beside the recliner) as he goes down. Then, in the next shot facing the door, that white lawn chair is upright (not the yellow table chairs), but in the next shot it's lying on the floor again. (00:32:40)
The Uniform - S2-E11
Character mistake: While handcuffing an auxiliary officer in his apartment, there is a poster on the wall reading, "attention military personal..." Personal is misused. It should read "attention military personnel." (00:16:02)
Continuity mistake: During the stakeout of the apartment building, in the exterior shots of the Clyde Motorcycles shop, Danny is peeking out through a ripped paper opening within the letter "D" in Clyde. However, in the interior shots the black tape letters of the word Clyde differs. The paper is ripped between the two letters "D" and "E" and that space within the "D" is blocked with molding, making what is in the exterior shots quite impossible. (00:15:40)
Visible crew/equipment: When Danny and Baez are at the scene of the firebombing while it's raining, in the second shot as they walk toward the eleven body bags, three nylon T-markers (yellow, red, and green) are visible on the wet ground where Baez, Danny, and Molina will be standing in the following shots. (00:02:45)
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)
Visible crew/equipment: When Eddie and Jamie stop to help the woman holding the boy, in the exterior shot as Jamie gets into the back of the RMP with the young boy, the reflection of camera equipment is visible on the window. (00:04:55)
Visible crew/equipment: After Anthony drives the Porsche 911 into the garage, in the shot facing Erin and Anthony just as Jimmy gets into the car, the green T-mark, the red tape mark, and blue tape mark are visible on the floor.
Officer Down - S1-E4
Factual error: Danny and Jackie Curatola are with ESU to make an arrest at a garage. They are behind cover with their weapons drawn. Although there is no suspect shooting at them, both Danny and Jackie have their fingers on the trigger, which is against police training unless you are going to engage a subject by shooting your weapon. The ESU officer right next to them does not have his finger on the trigger. (00:38:04)
Parenthood - S2-E14
Continuity mistake: In his office with Garrett, Frank reaches for his cup of coffee twice, and moves his foil-wrapped breakfast sandwich from the top of a stack of blue folders to the top of a newspaper. However, in the next shot, the egg sandwich is back on top of the stack of blue folders. (00:06:15)
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)
Continuity mistake: Part way into the episode they show the front of Jamie's Ford police car and the car number on the front plate, but when they pull up to the court house to talk to his sister, it's a Chevrolet police car with a different number on the front. (00:09:05 - 00:09:40)
Visible crew/equipment: At the safe house, while Danny and Waylon are alone with Rodriguez they "convince" him to call off his men, and in the last shot of this scene as they head out the door, the reflection of a crew member (presumably the camera operator) becomes visible on the picture hanging beside the door. (00:39:20)
Continuity mistake: While Danny and Waylon Gates are with Rodriguez at the safe house, showing him the photograph of his daughters, during this scene there is no picture hanging on the wall beside the door, but as they lead Rodriguez out in the last shot of the scene, a picture suddenly appears on that wall. (00:37:30 - 00:39:20)
Continuity mistake: The Reagan men sit at the table for a drink. Jamie's glass moves towards/away from him in different shots. (00:23:15)
Continuity mistake: While Danny and Baez are questioning Damian about Mason's whereabouts, Damian's right handcuff switches to the opposite way depending on the angle of the shots. Either the single metal bar faces up or the double bar faces up, which is quite impossible to change when it's locked around his wrist.
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.