Mexican authorities sent the U.S. teenager who used an "affluenza" court defense after killing four people while driving drunk in Texas back to the United States to face court proceedings.

"Ethan Couch, who entered at the Las Agujas immigration station ... after being found to be in an irregular administrative situation, was transferred this morning to the Mexico City International Airport," said the National Immigration Institute, or INM, in a statement.

Couch left Mexico at 8:50 a.m. on a commercial flight for Dallas, where he will be taken into custody by U.S. authorities.

He was transferred on Dec. 28, along with his mother Tonya Couch, to an INM holding center in the western city of Puerto Vallarta, although his mother was quickly sent back to the United States after posting bail.

However, Ethan Crouch's Mexican attorney - Fernando Benitez - filed a motion to avoid his deportation, thus delaying his return.

In 2013, the then-16-year-old Couch killed four people in Texas while driving drunk, but he managed to avoid jail after a psychiatric diagnosis claimed that he was spoiled into a sense of irresponsibility by his wealthy parents, a condition the psychiatrist called "affluenza."

A judge sent him to a rehabilitation center and sentenced him to 10 years of probation during which he was prohibited from driving, taking drugs or drinking alcohol.

However, a social network video in December showed him attending a party where alcohol was served, a violation of his probation.

Subsequently, he and his mother fled to Mexico and were eventually detained in Puerto Vallarta, a popular destination for cruise ships. EFE