Ethan Couch is seen in a Feb. 5, 2016 booking photo released by the Tarrant County Sheriff's Department in Fort Worth, Texas. (Tarrant County Sheriff's Department/Handout via Reuters)

A Texas teenager who used an "affluenza" defence in a fatal drunken-driving wreck was moved to an adult jail Friday to await a hearing over whether to transfer his case to the adult system.

Ethan Couch, 18, was initially booked into a juvenile detention facility after he was deported from Mexico on Jan. 28. He will stay in the Tarrant County Jail at least for another week, though his case remains in the juvenile court's jurisdiction.

He was placed in a single cell for his own protection, said Tarrant County Sheriff Dee Anderson. No bond amount was listed on his online jail records, Reuters reported.  

Authorities say he and his mother fled the U.S. in December, as Texas prosecutors investigated whether he violated his probation in the 2013 wreck that killed four people.

Mother out on bond

Couch's mother, Tonya Couch, is charged in Texas with hindering the apprehension of a felon. She was released on bond in January after being fitted with an electronic ankle GPS monitor. According to an arrest warrant, she told her estranged husband, Fred Couch, that he would never see her or their son again before fleeing.

If his case is moved out of the juvenile system, the judge could order Couch to spend up to 120 days in jail plus the remainder of his 10-year probation as part of an adult sentence, according to Tarrant County District Attorney spokeswoman Samantha Jordan. If he violates probation during that time, he could get up to 10 years in prison for each of the four people killed in the drunken-driving wreck.

With files from Reuters