Can my brother be fined $15,000 for leaving the state while his personaly injury suit is pending?

There are no fines for leaving the state while a plaintiff in a civil case in Colorado - my office routinely represents out-of-state plaintiffs in Colorado state and federal courts. It would seem there is a lack of communication between your brother and his attorney - perhaps the attorney is concerned about sanctions if your brother is not available for a scheduled deposition or IME, but this should be discussed between the attorney and client and a plan agreed to. If effective communication cannot be re-established between your brother and his attorney, he may wish to seek other counsel.