There are many sex crimes one can be arrested for in Jacksonville and all of Florida. In addition to committing the actual offense, you may be committing a crime if you don't report a sexual battery (rape).
If you see the someone rape someone else and:
1. have reason to believe that you saw the commission of a rape;
2. have the present ability to get assistance for the victim by immediately reporting the sex crime to the police;
3. do not call the police;
4. you would not be threatened with any harm if you called the police;
5. you are not the husband, wife, grandparent, child, grandchild, sister, or brother of either the suspect or victim; and
6. you are not the victim,
you can be arrested for a first degree misdemeanor in Florida. This crime is punishable for up to one year in jail and a fine.