Couch seemed "fine" and "in good health," the sheriff said.
"He was very calm. He was very quiet, very passive, not at all argumentative or resistant. He followed every direction. His only request is he was hungry and wanted something to eat," Anderson said. "He was as compliant and as docile as anyone we have ever seen coming into a facility."
Couch landed in Dallas before noon and is scheduled to attend a detention hearing Friday because the law requires a hearing within 24 hours, the sheriff said. Couch was scheduled to be medically screened and assigned to a housing unit at Tarrant County Juvenile Detention Center, he said.
"We hope justice can now be served for those four victims and their families," Anderson said.
Because Couch is 18, Anderson said he'd prefer to lock him up in an adult facility, but that issue may not be decided until Couch appears before a Tarrant County judge February 19. That hearing is slated to determine whether Couch's case can be transferred to an adult court, the county district attorney's office said.
Representatives from Mothers Against Drunk Driving will be in the courtroom, the organization said in a statement.
"Couch's actions are not that of a child, and we will continue our petition ... to move Couch's case from juvenile to adult court. Couch may be back to fight his battle in court, but MADD is here to continue fighting 'Affluenza.' We must ensure Couch gets prison," said Colleen Sheehey-Church, the group's national president.
Texas authorities have expressed outrage
that Couch, who got sentenced to 10 years probation but no jail time, had gone AWOL.
Couch has fought his forced return to the U.S. in Mexican courts after he and his mother were nabbed in the Pacific resort city of Puerto Vallarta on December 28, weeks after his probation officer last made contact with him
But on January 19, his lawyer Scott Brown told reporters that his Mexican counterpart filed a document that would "release an injunction and let the (transfer) process go forward."
Tonya Couch, the teenager's mother who was charged with hindering his apprehension, returned to the United States after the pair's capture
-- first to Los Angeles and then to the family's home state of Texas. She was released from jail on January 12
after posting $75,000 bond, CNN affiliate KTVT reported.
Her son was 16 years old on June 15, 2013, when he drove a pickup into a group of pedestrians on a road in Burleson, south of Fort Worth, killing all four and hitting a parked car. Two people riding in the bed of the teen's truck were severely injured after being tossed in the crash.
During his trial months later, Couch's lawyers argued that the teen's parents shouldered some blame for the crime because they never set limits for their son, giving him everything he wanted. A psychologist who testified for the defense claimed Couch had "affluenza," suggesting he was too rich and spoiled to understand the consequences of his actions.
Judge Jean Boyd decided after that trial that Couch wouldn't get jail time, instead sentencing him to probation. She didn't release him to his parents, though, saying that she'd work to find the teen a long-term treatment facility.
Still, Ethan Couch did end up back with his family. And -- after video surfaced on social media showing him at a party where alcohol was being consumed, which would have violated his probation -- he ended up in Mexico with his mother.
The U.S. Marshals Service tracked Couch, who turns 19 in April, using a cell phone linked to him, according to an official briefed on the investigation. They found him with a new look, his reddish blond hair and goatee having been dyed a dark color.
Last week, Brown said
in a hearing on Couch's status as a juvenile that the case shouldn't be allowed to proceed because there was no proof that Couch "voluntarily absented himself" from being at the hearing.
When asked by CNN whether Couch was taken against his will to Mexico, Brown replied, "I don't think that's what I said. As far as Ethan being taken against his will, we are examining the facts, investigating the facts."
In a statement released Thursday, Couch's lawyers said they are optimistic that he will comply with all court-imposed terms and conditions going forward. He was on probation for intoxication manslaughter.