If it was vouchered as arrest evidence the DA would have to release it.
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If you received a property receipt for the money than you need a release from the DA and you can get it back. If not, than the money was likely kept as evidence, and It is possible that in exchange for the plea offered to you by the DA you agreed to forfeit the money. If the money was taken as evidence and your case has been disposed and you did not agree to forfeit the money, then the DA must start a civil lawsuit to cause you to forfeit the money. If the DA starts a civil lawsuit to try to obtain the money you can either defend the lawsuit or have an attorney try to negotiate a settlement where you may get some of the money back.