Deliberate mistake: In the episode "Bunk," a man goes in the house looking for his cat. When the cat releases the fumes, it jumps down, but when the man dies, the cat is nowhere to be found. The cat is not mentioned ever again in the episode either.
Deliberate mistake: When they are trying to find out who the blogger is, they back trace to the IP address the person is using, the IP address they find starts with 310, the highest number any octet of an IP address can be is 255.
By the Book - S10-E6
Deliberate mistake: When the CSI team reported to the island to find the dead body hanging upside down, they kept repeating how the body had been completely drained of blood. Yet, every time they showed the body, the jugular vein distention was very obvious. This could only occur in a live body or one still full of blood. Not a blow your socks off type of error but one very noticeable by anyone in the medical profession.