Unindicted co-conspirator is a nonsense term, legally-speaking. Prosecutors lacking evidence that will hold up in other than a kangaroo court throw this term up to impress upon ignorant bystanders that the peasant whose life they can’t blow up on a whim, i.e. based on the fertile imaginations of politically-ambitious prosecutors alone, is a bad guy.
If you are a co-conspirator in a crime, you should be indicted.