No. That is the thing. The money is guilty of being dirty until the money's owner proves otherwise. Usually two things happen:

1. The owner decides it is not worth the hassle. 2. The government usually settles bogus seizes because they don't want case law building up over this subject.

You can be the rap but you can't beat the ride. The money is confiscated because the police think it was ill gotten. If you doubt they have enough proof you can bring that up at the trial.