A verb for helping a criminal without knowing it

Someone who helps a criminal without knowing it is referred to as an unwitting accomplice (unwitting means not done on purpose and accomplice means a person who helps another person commit a crime):

She was an unwitting accomplice to tax fraud. (She didn't know that she was helping someone to commit tax fraud)

dupe. TFD

n. A person who is easily deceived or is used to carry out the designs of another.

tr.v. duped, dup·ing, dupes To deceive (an unwary person).

As in: Y=criminal. X=dupe

X was duped by Y into participating in a crime.

stooge

noun
a person who serves merely to support or assist others, particularly in doing unpleasant work
"you fell for that helpless-female act and let her make you a stooge"

verb
move around aimlessly; drift or cruise.
"she stooged around in the bathroom for a while"

(in magic tricks someone is called an "instant stooge" when they are used in a trick to make it work without knowing they are helping ie activating a prop or reacting thinking one thing is going on when the audience sees something else going on)

Depending on the intentions of the criminal, "patsy" might be a good word for it. "Pigeon", "goat", "scapegoat", "pawn", and "dupe" might work in the same context as well.

I believe the term that you can use is "unintentional accessory".

The definition for "accessory" in a legal sense is defined by Collins as:

3. [H]elping in an unlawful act.

Additionally, you can find this term used in literature. For example:

... If the law has been outraged, the gentleman has been at least an unintentional accessory and whether this fact...

Hope this is helpful!