You may have two primary defenses to a charge of criminal embezzlement of a rental vehicle. The first defense involves a lack of intent to steal. For example, if you rent a car, and a personal emergency arises that prevents you from returning the vehicle by the end of your rental period, you might argue that you did not have an intent to permanently deprive the owner or rental company of the vehicle. This defense can be tricky, since you may need to show that you intended to return the vehicle at your first available opportunity.
The second defense to criminal embezzlement charges is establishing that you had consent – or a good faith belief that you had consent – from the owner of the vehicle to remain in possession. This might occur, for example, if you call the car rental company and ask to extend your rental. You might have been mistaken in your good faith belief that your rental period was extended, or the car rental company may have made a record-keeping error and failed to update their system to reflect your extension, leading the company to list your car as overdue.