Because civil asset forfeiture is civil in nature, the State does not need to prove that any crime occurred. The State must prove only by a preponderance of the evidence that your property is contraband.
"Preponderance of the evidence" means that the State needs to show that your property was more likely than not used (or intended to be used) in the commission of a crime. For example, money found in a drug lab may meet this burden of proof, even if there is no evidence that it was used in a specific drug transaction.
Fortunately, even if the State can meet that burden, there are “defenses” that you can use to keep your property from being forfeited. See Question 18.
In our example, the presence of several baggies of marijuana in the car might lead the court to conclude that Steve more likely than not received the money as the proceeds of a drug sale. Steve’s receipt from the check casher would suggest that the money was not proceeds of a crime.