Detective Carson fails to arrest "JJ" Jackson's father on the grounds that his rape victim had been pressured into dropping her charges and thus there was no complainant. That makes no sense. The CSI lab has obtained DNA evidence that Scott Jackson has committed rape, a very serious felony. They also have evidence that the victim was dosed with GHB, adding a poisoning charge. The crime lab is therefore obliged to inform the police, who would of course arrest the suspect.