Lawyers for a US teenager who used an "affluenza" defence in a fatal drink-driving wreck have turned to the Texas Supreme Court in a bid to secure his release from jail.
The motion filed on behalf of 19-year-old Ethan Couch argues that a judge had no authority to sentence Couch to nearly two years in jail after his case was moved from juvenile to adult court.
Couch's lawyers argue that the judge only had jurisdiction over criminal cases and that juvenile matters are civil.
Couch was given 10 years' probation after drunkenly crashing into a car parked on the side of the road in June 2013, killing four people. He was 16 at the time. He later violated his probation.
In December, it was revealed the teen threw a going-away party with his mother, Tonya Couch, before they fled to Mexico.
Couch was sporting a newly dyed mop of brown hair when he and his mother were tracked down in the resort town of Puerto Vallarta. Tonya could face up to 10 years' prison for helping her son elude law enforcement officials.
The case attracted worldwide attention because Couch's lawyer advanced the "affluenza" theory in his defence: that he was so pampered by his rich parents, he had no concept of responsibility.
The American Psychiatric Association does not recognise "affluenza" as a medical diagnosis.
The victims of the crash were Breanna Mitchell, 24, whose SUV had broken down; Brian Jennings, a youth minister who had stopped to help; and Hollie Boyles, 52, and her daughter, Shelby Boyles, 21, who had come from their house to assist.
Twelve people were injured, including Sergio Molina and Solaiman Mohman, teens who were Couch's passengers.
Couch had a blood-alcohol level three times the legal limit and had traces of Valium in his system, a court heard.