The DA is the one deciding to press charges, the parents are only the reporting party. Florida is one of the harshest states in the country when it comes to protecting minors; it's sort of the political "pet project" these days, and for very good reason.
The relationship, in the eyes of the law, was NOT consentual, because a 15 year old cannot, by definition, GIVE consent. Even if she begged and pleaded, the burden was on the legally recognized ADULT to know the true age of the person he was sleeping with.
She'll be getting in plenty of trouble with her parents. He'll be getting in trouble with the courts.
Actually, in Florida, he'd be looking at 15 years PLUS sex offender registration once released.
Mental incompetency may or may not play a factor in the case, but typically it won't come into play until sentencing (it COULD be a mitigating factor that could either lessen the sentence, or provide for "alternative" sentencing like being put into confinement in a mental health facility, or some combination thereof) - but in and of itself if he's high functioning enough to be able to "date", he's competent enough to be charged. The DA obviously feels he had the capacity to know better than to get involved with a minor (even if he didn't check any further than her telling him her age), otherwise they wouldn't bother pursuing the criminal case. If he substantially lacks the ability to tell right from wrong, that is a point his attorney can argue on his behalf after reviewing his medical history and mental health evaluations.
Since he's an adult on SSI, he should be able to get a public defender appointed. He can also check around town with several criminal defense attorneys, most will give at least an initial consultation for free.
