Am I liable if he does something and there is property damage or worse yet personal injury while he is driving the vehicle?

You could have some serious problems on these facts. By your statement that you and your brother are joint owners, I am assuming that you are both on title to the vehicle which would make both of you liable for any damage caused by a driver?s negligence or intentional behavior. Given that fact, you should both be named as insured parties in the insurance policy on the vehicle; if there is no insurance and your brother in driving the vehicle, that in itself is a violation of the law. Further, if the vehicle is encumbered by a loan, that contract also has a provision that the owners will maintain insurance at levels of coverage (property damage, personal injury and damage to the vehicle itself) set forth in the contract. If you brother negligently or intentionally causes damage or personal injury while driving the vehicle, and if you are both on title to the vehicle, you are both jointly liable for the damages and injuries. While I do not know the amount of your investment in the vehicle, if your brother is behaving erratically and you do not have an insurance policy with significant coverage, the best thing for you do to is go to the DMV office and do what you have to do to take your name off the title to the vehicle and make sure that removal is reflected in the DMV records. If your brother were to have an accident which caused serious injuries to someone, and if his medical records indicate the presence of depression and/or suicidal thoughts, you could be facing six-figure damages as a co-owner of the vehicle who took no steps to keep your brother from driving it.