If what you proffered is accurate, then it sounds like you may have yourself a good defense.
Generally, in order to prove battery, the State will need the victim to testify that s/he was struck against her/his will. There are instances where what would otherwise be hearsay are admitted, but I cannot imagine a circumstance where a hand-written statement by someone other than the declarant would be admitted into evidence.
Personally I suspect that something is missing or incorrect., but if I were you then I'd get myself into a criminal defense attorney's office and let someone with training and experience make sense of your situation.
Although I practice primarily in Miami-Dade County you are welcome to contact my office for a referral or two, or you can search the Florida Association of Criminal Defense Lawyers website by locality (please see http://www.facdl.org/ - and click on the "Find A Lawyer" tab).
Either way best of luck!
I don't really understand the situation from your question but the answer is that a witness does not have to write their own statement. Witnesses have others write their statements all the time either because they cant read/write English, or because they are injured or to excited to write. So that fact that the witness didn't write the statement , and only signed it is meaningless to your case.
For more information or to set up a free initial consultation contact the Mangrum Law Firm at 407-349-7474 or MangrumLaw@gmail.com. This answer does not, nor is it intended to, create an attorney-client relationship. It is offered for informational purposes only. Please consult with a licensed attorney before making any legal decisions.
It certainly sounds like something you should challenge. There are occasions where someone will record the statement of another person, and it would be considered proper. If the witness is illiterate, or physically incapable of writing, someone else can record a verbal statement in writing and then have it attested to.
Regardless of the details of the witness statement, you need to hire an attorney and challenge this. You do not want to go through life with a battery conviction on your record.