The Federal Bureau of Investigations (FBI) and US Marshals have joined the manhunt for a wealthy Texas teenager who avoided prison time for killing four in a drink driving incident because he was afflicted with "affluenza". The search for Ethan Couch was launched after he skipped a mandatory meeting with his probation officer.

The 18-year-old was placed on Tarrant County's most wanted list after missing the meeting with his probation officer, which prompted a warrant for his arrest on 11 December. According to Reuters, Couch has been entered into a national fugitive database search. "He has no idea what he faces when he is found," Tarrant County Sheriff's spokesman Terry Grisham said.

Couch was sentenced to 10 years probation for intoxication manslaughter for the 2013 crash. The teen was sparred a jail sentence after a psychologist testified on his behalf that he suffered from "affluenza". The psychologist claimed Couch could not take responsibility for his actions because of his parent's wealth.

Dallas defence attorney Nicole Knox told CBS Dallas Fort Worth that Couch's mother could face charges if the pair are found. She said if law enforcement could present facts to the District Attorney's office that the mother had in fact aided in Couch violating probation, "then there might be a basis for her obstructing justice."

Knox said Couch could also face severe consequences. "It would be up to a judge whether or not his probation has been violated. The judge could find that he violated his probation and terminate his probation and sentence him up to ten years in prison," she said.

Couch is still a juvenile under the Texas legal system, but could potentially face real prison time. "Any mess-ups from now on, he's going to be over with us," Grisham added, according to the Dallas Morning News. "He's going to see what the big-boy jail is like." However, with Couch nowhere to be found, authorities fear he may have fled the US.

A video released earlier in December claimed to show Couch playing beer pong, violating his probation. The district attorney's office said it was still investigating the video and did not comment whether he violated probation. The Dallas Morning News reported that the district attorney's office has requested the case be moved from juvenile court to adult court after the teen turns 19 in April.