You cannot. The State Attorney's Office is the agency in charge of following through with the charges, even if you ask them not to. You may tell the State Attorney your preferences regarding the charges and the State Attorney may dismiss them, but the State Attorney does not have to. It may want to continue the prosecution forward. What has occurred before, however, is that the State Attorney needs your cooperation and testimony before a judge and/or jury to convict your fiance. You must, of course, cooperate with the process, but if you do not, they usually will not continue with the case.
Hope the answer helped you.
Alejandro R. Lopez, Esq.
Law Office of Alejandro R. Lopez, P.A.,
2996 Edgewater Drive,
Orlando, Fla. 32804
Ph.: (407) 649-1404
Fax: (407) 649-9890
Your fiance should hire a lawyer ASAP. His lawyer can then interview you about what happened the night you were mugged. Once you and the lawyer have an opportunity to speak the lawyer can decide what is the best avenue to take.