Ethan Couch arrest: US runaway teen 'held farewell party'

Police released a mugshot of Couch, with his dyed hair

A teenager who was on the run after a fatal drink-driving crash held a farewell party before fleeing to Mexico, say police.

Officials in Texas said that Ethan Couch, 18, and his mother Tonya, planned his escape out of the country.

They were arrested in the resort town of Puerto Vallarta on Monday night.

Couch made headlines by avoiding jail for the crash, which killed four people, after claiming his privileged upbringing was to blame.

An arrest warrant was issued earlier this month for Couch after he failed to report to his probation officer.

Police believe he fled because he had broken the terms of his probation, which prevented him from drinking.

At a news conference on Tuesday, Tarrant County Sheriff Dee Anderson said a warrant would be issued for Tonya Crouch on charges of hindering and apprehension.

She and her son planned their disappearance and even held a going-away party, he said, which showed how "pre-meditated" his escape was.

Couch dyed his hair and beard to change his appearance, said the sheriff, adding that it clearly did not work.

There is no evidence that the father was involved but the investigation continues, he added.

Tonya Couch is accused of assisting his escape

Wanted posters were issued for Ethan Couch

In 2013, when aged 16, Couch crashed into a stationary car while drunk, killing four people and injuring several others.

He pleaded guilty and a judge sentenced him in juvenile court to 10 years' probation and a stint in a rehabilitation centre.

A psychologist at this trial successfully argued that his privileged upbringing - an unrecognised condition known as "affluenza" - meant his parents had not properly instilled in him a sense of responsibility for his actions.

Texas authorities will now try to move his case from the juvenile system so that he can be treated as an adult - raising the possibility of a prison sentence.