I would strongly recommend you consulting with a Tampa criminal defense attorney. Given the facts of your case, there may be motions to suppress or a (c)(4) motion to dismiss availble, which would significantly strengthen or even eliminate the case against you. It is impossible to estimate the liklihood of the success of these motions without know more about your case, which I recommend you not post in a public forum like Avvo. Consult a Tampa criminal defense attorney immediately, so they can begin investigating your case.
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
It sounds like a case of constructive possession which is difficult for the state to prove absent admissions. I would get your aunts prescription to an attorney ASAP so they can compare the script to the pills found in the car. If they match up your aunt will need to be listed as a witness. Feel free to contact my office for a free consultation.
You definitely need to challenge the evidence. As the other lawyers have suggested, this will require various legal motions to bring the issue properly before the court to be ruled on. However, I disagree with the suggestion by one of the lawyers that constructive possession cases are difficult to prove. Especially because in America in 2012, when you walk into court you are usually presumed guilty until you can prove yourself innocent, which is not the way its supposed to be but is the sad truth.