Milestones - S9-E12
Other mistake: First we see Jamie in a Ford CVPI with license plates 7554 like a couple of times before in the show, a minute after he's seen exiting a 2015 Ford Taurus with plates 82399. He answers a 10-85 while supposedly driving in the CVPI but somehow he manages to change in less than a minute to a Taurus. We see the exterior of the car, but the car's interior corresponding to the Taurus is seen a few seconds earlier. (00:03:35 - 00:04:20)
Milestones - S9-E12
Continuity mistake: Jamie is arresting a subject after he drops a knife. Jamie kicks the knife away from the subject and it lands next to the brown box and under the red wording on the box. In the next frame, the knife is now just behind Jamie's right knee. (00:05:10)
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.