The proof presented by the State will depend upon the allegation(s) in the affidavit of probation violation.
For example, if you are accused of violating your probation by committing a technical violation(s) then the State will likely simply call your PO and your PO will testify as to the nature of the technical violation (failure to comply with whatever condition(s) that may apply - maybe failure to attend classes or make payments or move or travel without permission, etc.).
If the violation is based upon a new arrest then the State will bring in the arresting officer or the victim and present evidence that you "failed to remain at liberty" during the probationary period. (Note that they do not have to prove that you are guilty in the new case beyond a reasonable doubt - that is another matter for another hearing / trial - rather, the State merely has to prove that you violated the "do not get arrested" condition of your probation.)
The burden of proof is, as you have correctly identified, "a preponderance of the evidence", and, brutally, unlike in criminal trials hearsay is completely admissible in PVH's (although it cannot be the sole basis for the Court to rely upon in violating you - there must be something above and beyond hearsay), but the State will be required to make a sufficient showing that a) you willfully violated and b) that your violation was substantial ("willful and substantial" are the standards for PVH's in FL).
So, say for instance that you are being violated because of failure to make restitution payments. The State would have to show that you had the ability to pay and chose not to pay, and also that your failure to pay was substantial (if you owed $1,000.00 and had paid $900.00 but not the balance it may or may not be considered "substantial").
Probation is better than incarceration, until you are violated, and then it sucks. Make sure that you are represented by experienced Kissimmee area criminal defense counsel as the same will greatly increase you odds at success.
Although I practice primarily in Miami-Dade County you are welcome to contact my office for a referral or two, or you can do a location search here on Avvo 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!
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Both of my colleagues are correct, the VOP affidavit isn't enough. They will bring in witnesses and your probation office. The rules of evidence are essentially the same as a jury trial with one major exception, hearsay is admissible. It is worth noting the violation cannot be based solely on hearsay, some other evidence is required. Our firm has handled matters in your area and offers free case consultations. Good luck, have a good rest of the weekend.
This answer does not, nor is it intended to, create an attorney-client relationship or constitute attorney advertising. Rather, it is offered solely for informational purposes. The facts of each case are different and unique, it is critical to consult with qualified counsel with whom information can be shared and assessed under attorney-client privilege, so that competent and quality advice can be obtained on which you can make informed decisions
The type of proof, as mentioned in the other answers, will depend on the type of violation. As you know, the standard of proof is by a preponderance of evidence rather than beyond a reasonable doubt. However, generally if the violation is based upon anything other than a technical violation to which the probation officer can testify directly to, or, alternatively, the probation officer claims the probationer has misrepresented something relating to a condition of probation to the probation officer, there must be more than hearsay to violate someone's probation in Florida. However, no attorney can give you adequate advice without reviewing your affidavit of violation of probation. My suggestion would be that you contact an criminal defense attorney in your area to consult with.