FORT WORTH, Texas (Reuters) - America’s “affluenza” teen had his case transferred to the adult court system on Friday, where 18-year-old Texan Ethan Couch faces decades behind bars if he violates a probation deal that kept him out of prison for killing four people while driving drunk.

Judge Tim Menikos in Fort Worth transferred probation supervision for Couch, who was convicted in juvenile court in 2013 on charges related to the crash earlier that year, when he was 16.

Couch, who fled to Mexico last year after an apparent violation of his probation agreement, is set to serve at least 120 days as part of the transfer of the case to the adult system, his lawyers said after the hearing.

Couch will remain in jail for now in solitary confinement, Tarrant County Sheriff Dee Anderson said.

“He always acted like this was some type of game and that his wealth and privilege would protect him,” Anderson said after the hearing, adding being in jail “has truly humbled him.”

Prosecutors wanted the case moved to the adult system, where Couch could serve up to 40 years in prison for any future probation violation.

Couch appeared in court wearing a red prison jumpsuit and answered a few simple questions during proceedings that lasted about 10 minutes.

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At his trial in juvenile court in 2013, a psychologist testified for the defense that Couch was so spoiled he could not tell right from wrong. The psychologist described the affliction as “affluenza,” a term that quickly became a media buzzword.

Couch was sentenced to 10 years probation, during which he was to remain alcohol- and drug-free. The sentence sparked outrage from critics who ridiculed the affluenza defense and said his family’s wealth helped the teen stay out of jail.

Couch has been in custody since he was brought back from Mexico last month. With his mother, Tonya Couch, he fled Texas in December, apparently to avoid arrest for violating the probation deal after video on social media appeared to show him at a party where alcohol was being consumed.

Couch had a blood alcohol level nearly three times above the legal limit for an adult when the pickup truck he was driving struck and killed a stranded motorists and three people who stopped to assist.

Tonya Couch faces up to 10 years in prison for helping her son flee.