Sheriff: Texas 'affluenza' teen had 'going away' party before fleeing country, mother to be charged

This Dec. 28, 2015 photo released by Mexico's Jalisco state prosecutor's office shows who authorities identify as Ethan Couch, after he was taken into custody in Puerto Vallarta, Mexico. U.S. authorities said the Texas teenager serving probation for killing four people in a drunken-driving wreck after invoking an "affluenza" defense, was in custody in Mexico, weeks after he and his mother disappeared. (Mexico's Jalisco state prosecutor's office via AP) less This Dec. 28, 2015 photo released by Mexico's Jalisco state prosecutor's office shows who authorities identify as Ethan Couch, after he was taken into custody in Puerto Vallarta, Mexico. U.S. authorities said ... more Photo: AP Photo: AP Image 1 of / 20 Caption Close Sheriff: Texas 'affluenza' teen had 'going away' party before fleeing country, mother to be charged 1 / 20 Back to Gallery

Texas "affluenza" teen Ethan Couch and his mother Tonya Couch staged a "going away" party before they fled to Mexico, authorities in North Texas said Tuesday.

Ethan Couch, on probation for killing four people in a drunken driving crash in 2013, and his mother were detained in the Pacific Coast resort city of Puerto Vallarta on Monday. Both are in the custody of Mexican authorities but are expected to return to the U.S. Tuesday.

The 18-year-old and his mother appeared to have planned their disappearance and even had a "going away" party prior to driving their truck to Mexico, Tarrant County Sheriff Dee Anderson told reporters during a Tuesday morning press conference in Fort Worth.

RELATED: 10 facts about the 'affluenza' Texas teen Ethan Couch, who's on the run from the FBI

Tonya Couch, 48, will be charged with hindering apprehension, a third-degree felony punishable by a maximum 10 year sentence, Tarrant County District Attorney Sharen Wilson said at the press conference. A warrant has been issued for her arrest.

"Her entire focus has been on protecting Ethan, her entire focus has been on making sure he didn't see any justice done, making sure he was not accountable," Anderson said.

Ethan Couch was sentenced to 10 years probation in 2014 provided he abstain from driving, drinking and doing drugs. He was convicted in 2013 on four counts of intoxication manslaughter after drunkenly crashing into six people, killing four and injuring two.

The teenager's lawyers claimed he suffered from "affluenza," arguing that his parents had allowed him too much money and didn't discipline him.

A video surfaced on Dec. 2 of Ethan Couch apparently playing beer pong with a group of people, raising questions about whether his punishment should be changed.

Anderson said investigators believe the man in the video is Ethan Couch, but they have no definitive proof.

RELATED: 'Affluenza teen' Ethan Couch caught in Mexico with mother: CNN

Ricardo Ariel Vera, the representative of Mexico's immigration institute in Jalisco, told The Associated Press that Ethan Couch and Tonya Couch will return to Texas on a commercial flight to Houston on Tuesday.

Ethan Couch will go before a juvenile judge for a detention hearing on Jan. 19, Wilson told reporters.

At that time, Tarrant County prosecutors will seek to move his probation to adult court, Wilson said.

If Ethan Couch remains in the juvenile system, he will be incarcerated in a juvenile facility until his 19th birthday in April.

If the juvenile judge elects to move the 18-year-old's case to the adult system, his 10-year probation sentence would restart, Wilson said.

However, a state district judge could sentence Ethan Couch to 120 days in an adult detention facility as a condition of his probation.

"We are bound by the sentence he received by the juvenile judge in 2014," Wilson said.

RELATED: New Texas laws will go into effect on Jan. 1

Anderson and Wilson both criticized the sentence handed down by State District Judge Jean Hudson Boyd, who oversaw Ethan Couch's case.

"I believe she did what she thought was right at the time," Wilson said.

Boyd resigned in December 2014. State District Judge Timothy A. Menikos now resides over the 323rd District Court, where Ethan Couch's trial took place.

jfechter@mySA.com

Twitter: @JFreports