Visible crew/equipment: When Danny gets off the phone he tells Baez that a Port Authority cop has detained their guy, and at the start of the next shot facing Baez, the reflections of the moving boom pole/mic and the boom operator are visible on the glass, at the right side of the screen. (00:02:20)
Visible crew/equipment: After Frank tells Garrett to set up the meeting with Thomas and agrees to play nice, when it cuts to Erin as she walks toward Zach and the AG, the T-mark and white tape mark are visible on the floor in front of the two men. (00:01:50)
Visible crew/equipment: When Eddie comments that the Rough Tough Cream Puff made a collar, she and Jamie walk up the hallway, and before Eddie reaches the doorway we can see the red tape mark on the floor as we hear Marcus brag, "mad fast." (00:15:55)
Visible crew/equipment: After Danny and Baez get the hospital physician's rundown on Joe's condition, when the partners reintroduce themselves to Joe the reflection of the boom pole/mic is visible on the glass behind Danny.
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.