Deliberate mistake: When the runner is shot in the back of the head in the SUV, the bullet has come out the front of his head. However, blood is seen on the windshield instead of a bullet hole where the bullet would have continued to go through the glass.
Who Are You? - S1-E6
Deliberate mistake: A plumber is looking for a leak under the floor of a house, and sees the bones of a hand sticking out of the concrete wall at the side of the house. The concrete is flat, this is because in construction boards are put up and the concrete is poured in, so how were the fingers sticking out of the boards during construction? In reality, the fingers would be inside the concrete, the workman would see nothing, no plot for CSI.
Cool Change - S1-E2
Deliberate mistake: Willows collects fingernail scrapings from Holly's left hand in the morgue for DNA matching to Holly's shooter. In the flashback, Holly uses her right hand to scratch her assailant while her left-hand remains gloved. (00:32:47 - 00:36:22)