The Texas teenager who used an "affluenza" defense in a fatal drunken-driving wreck will remain in a juvenile detention center as he awaits a judge's ruling on transferring his case to the adult court system, a judge ruled Friday.

Ethan Couch, 18, was booked into a juvenile detention facility in Fort Worth after he was deported from Mexico on Thursday. Authorities believe he and his mother fled the country as Texas prosecutors investigated whether he may have violated his probation in the 2013 wreck that killed four people.

Judge Timothy Menikos sided with Couch's attorneys during a court hearing in Fort Worth, saying the 18-year-old Couch could stay at the juvenile center. Prosecutors wanted Couch moved to an adult jail ahead of a hearing next month that will determine whether the case is transferred to the adult system, where Couch could face time behind bars.

Tarrant County Sheriff Dee Anderson said Thursday that he wanted Couch moved to an adult jail, given his age and the severity of his offenses. Couch was 16 at the time of the fatal accident, so the case is being handled for now in juvenile court.

"He's certainly capable of understanding now what's going on, and I'd feel better if he was there," Anderson said.

During the sentencing phase of the 2013 trial, a defense witness argued Couch had been coddled into a sense of irresponsibility by his wealthy parents. The expert deemed the condition "affluenza," which isn't recognized as a medical diagnosis by the American Psychiatric Association and drew widespread derision.

The teen was later sentenced to 10 years' probation, which including barring him from drinking or leaving Tarrant County, Texas. Prosecutors and law enforcement officers blasted the sentence as too weak.

In December, Couch and his mother disappeared after an online video appeared to show Couch at a party where people were drinking. They were apprehended in the Mexican resort city of Puerto Vallarta on Dec. 28, after a call for pizza delivery tipped off authorities to their whereabouts.

Couch initially fought deportation, but he dropped the fight this week. His mother, Tonya Couch, was deported last month and is charged in Texas with hindering the apprehension of a felon. She was released on bond this month after being fitted with an electronic ankle GPS monitor.

If Ethan Couch's case is moved to adult court in Texas, the judge could order Couch to spend up to 120 days in jail for violating his probation and then finish the remainder of his 10-year probation sentence, according to Tarrant County District Attorney spokeswoman Samantha Jordan. If he were to violate his probation again, he could get up to 10 years in prison for each of the four people killed in the drunken-driving wreck.

If his case remains in juvenile court, he could be held in a juvenile detention center for violating his probation until he turns 19 in April, at which point he would become eligible for parole.