(at around 29 mins) Lt. Tragg (Ray Collins) is on the witness stand where he identifies two separately-made fingerprints of the defendant. One was taken from the murder weapon (a glass bookend) and the other taken at police headquarters. The side-by-side fingerprints, impossibly, are exactly the same in every respect.
After Paul Drake arrives and makes his distinctive "shave and a haircut" knock on the back door of Perry's office, he reports on his investigation of the murder victim's neighbor. During that conversation, the shadow of the boom mike can be seen on the wall to the left of his head.
Witness Luke Hickey's testimony is interrupted so Lt. Tragg can take the stand because he is wanted at headquarters and has to leave. When Tragg is done, he does not leave the courtroom and can be seen sitting there throughout the rest of the scene.