The parents make their report to police. Police will investigate/conduct interviews, and turn the case over to the state attorney's office. The SAO will be the one who ultimately decides if a criminal prosecution will occur. And in Florida, as you've already been told, they are RAPID about prosecuting sex crimes against those under 16, ESPECIALLY when the other party is OVER 16, even if only by a year. He's OVER 16, which means that he'd still fall within the "Romer and Juliet" exception to consent. The problem is that SHE is UNDER 16 - and her being under 16 means she's going to be treated as the victim; regardless of ANY other circumstances. He really needs to be planning for the state to be throwing the proverbial book at him, and all the issues (sex offender registration, restraining orders, etc.) that can go along with that process.

