Ethan Couch has returned from Mexico, having decided to forgo a fight against extradition back to the United States.

The 18-year-old Fort Worth resident whose trial for drunken driving brought us the term “affluenza” is likely to face a few more months in jail. He really ought to spend some years behind bars, but Texas law won’t allow it.

Couch killed four people two years ago — when he was still a juvenile — after getting roaring drunk and then driving his pickup. He got off with a probated sentence after his defense team brought in a shrink who said Couch’s upbringing by wealthy parents failed to teach him right from wrong.

Hence, came the term “affluenza defense.”

Couch then bolted to Mexico after violating the terms of his probation.

Who helped the kid? His mother. Tonya Couch already is back in Texas. She’s posted bail and awaits her fate.

No matter what happens to Ethan Couch, his mother deserves — and well might get — some serious prison time.

Given that state law won’t allow the court to throw Ethan Couch into the slammer for more than three or four months, it ought to look carefully at how complicit his mother was in enabling her bundle of joy to violate the terms of his probation and then flee to Mexico.

In a curiously ironic twist, Mommy Couch’s alleged complicity in this caper lends ghastly credence to what the shrink said at her son’s trial about how she and Daddy Couch didn’t teach their son about proper behavior.

It didn’t justify that ridiculously light sentence in the first place.

However, it does suggest that Tonya Couch needs to pay a stiff price if she’s convicted of aiding in her son’s flight from justice.