Regardless of who is driving, Illinois law appears to impose sanctions on the owner of a vehicle that is involved in an accident, if the owner does not at least have insurance relating to himself and his own driving. See 625 ILCS 5/Ch. 7, Art. II. For direct responsibility for an accident, Illinois appears to recognize common law vicarious liability, meaning that liability to the owner can result from such factors as knowingly entrusting the vehicle to a bad driver, but I don't see any provision which makes the owner automatically liable for a driver's actions.

Selling a jointly titled car is tricky if the co-owner isn't cooperative. But you probably have an equal right to possession, if you want to take control of the car. If sonny paid for the car, consider titling it over to him so that it isn't your problem any more.