Episode #3.6 - S3-E6
Factual error: Humphrey and the rest of the crew arrive on the murder scene, where Fidel is taking pictures of the body. With the knife fully planted inside the victim and pictures still to be taken, Fidel is already able to say that the knife has been wiped clean of prints; it's impossible that he could have already done such an assessment at that point.
Answer: There's probably no particular reason. Sets and props on long-running TV shows often change as needed and for various reasons throughout a series run.
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