Widespread Manhunt for Fugitive 'Affluenza' Teen

U.S. Marshals released a wanted poster for Ethan Couch and authorities declared his mother was a missing person.
4:40 | 12/22/15

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Transcript for Widespread Manhunt for Fugitive 'Affluenza' Teen
The rich and privileged teenager who killed four people in a drunk driving accident and got no jail time, after a novel ainfluenza defense, now reportedly on the run with his mother. Perhaps joining him as an accomplice. What's the next thing you recall? Waking up handcuffed to the hospital bed. Reporter: He's the rich teen whose drunken ride left four dead. There's four, five kids, kids laying in ditches and streets. Oh lord, oh, yes, there's another child in the ditch, oh my god. This guy killed four people. Paralyzed another. Reporter: And famously sparked the so-called affluenza defense. Affluenza? Too rich for jail. Reporter: She is the doting mom who infamously didn't rein him in. When is the last time you recall disciplining Ethan for anything? I don't remember. Reporter: Ethan couch, now 18 years old, and his mother, Tanya, reportedly fleeing authorities together. We believe that she's helping him and that she's assisting him. We need the public's help in locating this vehicle. Reporter: Perhaps in this tricked-out harley-davidson edition Ford pickup truck after undated video surfaced of Ethan attending this beer pong party, raising questions he might have violated his probation. To be a violation of probation they need evidence he was actually drinking. Not just at a party. Reporter: It began on a summer night in 2013 when couch, downing booze and pills, got behind the wheel of his father's red pickup truck. Speeding down the wrong side of the road, he lost control of the vehicle and plowed into a group of people. Just a recipe for disaster. Reporter: Richard Alpert, the assistant district attorney who charged Ethan with four counts of into saying manslaughter. Alpert wanted the poor little rich kid to do big boy time. We asked for 20 years. Reporter: Ethan pled guilty, then during sentencing adopted an unusual defense. Affluenza. He talked about the fact that the reason for this crime was he was a child of privilege. And his parents didn't say no to him. Reporter: The juvenile court judge sentenced it's than to ten years probation and time in rehab. Four dead, nine injured, and not a single day behind bars. What I really hate about this is not the nagging sense of wrongdoing and injustice. What I really hate is having this all dredged up, reopening the wound for these victims' families. Reporter: In videotaped depositions from a civil trial his parents admitted to allowing him to live on his own in this 4,000 square foot ranch house. These pictures from the weapon site zillow show a wet bar in a den, a pool out back. They let him drive a car from the time he was 13. You understood, if he was at any time under 16, he was never to be driving by himself? Yes. Nevertheless, you allowed that behavior to happen, correct? Yes. Reporter: Now has Ethan's mom gone insofar as to enable his escape? If we can find out she helped him at all, I assure you, we will file criminal cases against her. Reporter: Ethan's father Fred couch is cooperating with authorities. Telling them he hasn't heard from either of them in two weeks. I promise you, he is being tapped and surveilled. His money transactions, his cell phone, his home phone. Like nobody's business tonight. They are watching to see if he's transferring money to them. Not so much for his wife. They're esstranged. But his baby boy. Reporter: Following that troul cld lead authorities to exactly where Ethan and Tanya may be hiding out. You've got to find the money. You find the end of the money, you find the kid. Bottom line. Reporter: But that won't help much if they've left the country. There are around 100 countries that do not have an extradition treaty or agreement with the United States. Reporter: If they're caught, first-time charges for Tanya could be stiff. The mother may very well face jail time of her own. In some jurisdictions that's up to ten years. Depending on the degree with which you aid and abet the fugitive. Reporter: And Ethan may face what critics said he deserved long ago. In my opinion, he belongs in big boy jail. He belongs in adult prison. Let him get a taste of real prison and real adult justice. And maybe let him know that money and privilege don't buy you out of every circumstance.

This transcript has been automatically generated and may not be 100% accurate.

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