> A suspected bank robber gets arrested when the money is kept. The outcome of the arrest is a conviction or an acquittal, which (automatically) determines the fate of the money.

No, it doesn't. An accused bank robber could be acquitted of the crime of robbery and still found liable for the tort of conversion of property, and have to pay the money back to the bank.

(Additionally, either criminal or civil forfeiture may be available against the specific money involved, only in a criminal forfeiture case would the acquittal of the defendant on the criminal charges be dispositive. Generally, as I understand it, criminal forfeiture applies to a broader and more distant class of property relations to the crime, and therefore isn't used for the types of property to which civil forfeiture could be applied.)