AUSTIN, Texas (Reuters) - A Texas prosecutor is trying to place behind bars a teenager who killed four people while driving drunk but received a sentence of probation based partially on defense arguments that the youth was a victim of his family's enormous wealth.

Tarrant County District Attorney Joe Shannon said on Wednesday he will try to have the 16-year-old placed in juvenile detention for two lesser counts of intoxication assault that were not among the charges at his trial.

Shannon said in a statement that since no judgment was rendered on those, he will press the judge to reach a verdict. A legal expert said, however, that the teenager was unlikely to receive harsher punishment for lesser charges.

The case has set off an emotional debate, and not just in the suburbs of Fort Worth, Texas, where the deaths occurred in June, because a psychologist for the teenager said he suffered from "affluenza." The condition was described as one where a person feels shielded from responsibility by money, having led a life of privilege paid for by parents.

On December 10, Judge Jean Boyd sentenced the teenager to 10 years probation and ordered him to get therapy, a decision that led to a backlash among those who thought the family used its wealth to keep the teen out of jail.

"There has been no verdict formally entered in the two intoxication assault cases. Every case deserves a verdict," Shannon said.

Lawyers for the teenager were not immediately available for comment.

Under state law, the teenager could have been in custody up until his 18th or 19th birthday, but an expert on the juvenile justice system said it would be unusual for the teen to face time in a detention facility.

"If the judge gave probation for the four counts of intoxication manslaughter, it would be unlikely to give a harsher penalty for lesser charges," said Jessica Dixon Weaver, an assistant professor of law at Southern Methodist University in Dallas.

The two main candidates in a contentious governor's race, Republican Greg Abbot and Democrat Wendy Davis reached a rare moment of agreement, questioning the decision and saying they would consider changes to prevent it from happening again.

Psychologist G. Dick Miller, the expert witness for the defense who said the teen was suffering from "affluenza", later said he regretted his choice of words.

"I wish I had not used that term," he told broadcaster CNN this month. "Everyone seems to have hooked on to it."

Miller was not available for comment on Wednesday. He was on vacation until January, according to a message on his office phone.

The American Psychiatric Association, the leading organization for psychiatrists in the United States, does not recognize "affluenza" as a diagnosis.

The teen was driving a pickup truck when he ran down four people in June who were helping fix a vehicle along the road in the Fort Worth area.

The four killed were Breanna Mitchell, whose car broke down, Hollie and Shelby Boyles, who lived nearby and came out to help and youth minister Brian Jennings, who stopped to help.

At the time of the incident, the teenager had a blood alcohol count of three times the legal limit for an adult, prosecutors said. Prosecutors have come under fire for not trying the teenager as an adult.

The crash also severely injured two people riding in the teen's pickup truck, one of whom is paralyzed, prosecutors said.

Patricia Zapf, a forensic and clinical psychologist specializing in forensic psychological evaluation at John Jay College of Criminal Justice, said the "affluenza" defense has become a subject of ridicule in her professional circle.

"The only possibility is that maybe the judge in this case was either swayed by arguments, or had in the back of her mind that the family is going to pay one way or another," Zapf said.

The family is facing at least three civil lawsuits from the families of victims, who are seeking millions of dollars, according to Texas media reports.

(Additional reporting by Jana Pruet in Dallas and Elizabeth Dilts in New York; Editing by Grant McCool)