CORPUS CHRISTI, Texas (AP) — Investigators say three Houston teenagers have died and another was critically hurt in a South Texas traffic accident as they drove home from spring break.

The Texas Department of Public Safety says the wreck happened Sunday afternoon on Highway 77 near Corpus Christi when the car went out of control and hit an 18-wheeler.

Sgt. Nathan Brandley on Monday said distracted driving by using a cellphone for GPS was a factor in the crash as the teens headed home from South Padre Island.

Brandley says 17-year-old Jade Robinson and her 19-year-old sister, Brianna Robinson, died at the scene. Brandley says 18-year-old Brittanie Johnson died at a Corpus Christi hospital. The car's driver, 18-year-old Shelby Coleman, was hospitalized in critical condition.

The trucker wasn't hurt.

LIVINGSTON, Texas (AP) — Attorneys for a death row inmate from North Texas who shot to death a city employee who was taking photos of junk piled up at his family's property say their client is delusional and should not be executed because of his mental illness.

Adam Ward insists he was defending himself 11 years ago when he killed code enforcement officer Michael Walker outside the Ward family home in Commerce, about 65 miles northeast of Dallas. Ward, 33, is set for execution Tuesday evening in Huntsville.

"This man charged up and tried to attack me," Ward said recently from a visiting cage outside death row. "Long story short, my case is a case of self-defense, but there are cops there in that town that have tampered with evidence, they have removed evidence, they have added evidence to the scene."

Ward's lead trial attorney and court documents describe him as delusional.

In a videotaped statement to police following his arrest, Ward said he believed Commerce officials long conspired against him and his father, described in court filings as a hoarder who had been in conflict with the city for years. Evidence showed the Ward family had been cited numerous times for violating housing and zoning codes.

Ward's attorneys have asked the U.S. Supreme Court to halt the execution, renewing arguments that he is severely mentally ill and contending that his execution would be unconstitutional because of evolving sentiment against executing the mentally ill. The high court has ruled that mentally impaired people, generally defined as those with an IQ below 70, may not be executed.

State lawyers, who said evidence showed Ward's IQ as high as 123, said courts have not exempted mentally ill offenders from the death penalty and disputed Ward's arguments about changing attitudes regarding capital punishment of the mentally ill. The Supreme Court has held that mentally ill prisoners may be executed if they understand they are about to be put to death and why they face punishment.

Evidence of Ward's delusions, paranoia and bipolar disorder was presented at his 2007 trial and resurfaced in earlier unsuccessful appeals. The Supreme Court last October refused to review Ward's case.

Witnesses said Walker was taking pictures from the perimeter of the Ward property on June 13, 2005, when they got into an argument. Ward, who had been washing his car, sprayed the city worker with water from a hose.

Dennis Davis, Ward's trial lawyer, says the code officer told Ward that he was calling for back up, and in Ward's mind this meant police were on their way to kill him.

"He had no idea that was the exact wrong thing to say to that person," Davis recalled last week.

Walker pulled out his cellphone, made the call and waited near the back of his truck. Ward went inside the house, emerged with his gun and started firing.

Walker, 44, was shot nine times.

"Whenever you've been harassed, you take preventative measures if you have to," Ward told The Associated Press from prison, repeating testimony he gave at his trial that he believed Walker was armed. "I was matching force with force, when this man had pulled a gun on me and he pointed it at me and was fixing to shoot me, which is self-defense."

No evidence showed Walker carried a gun and Ward's trial lawyers never raised the issue.

"When I stepped in front of the jury, I said, 'I'm not going to be so callous and look you in the face and say my client didn't kill this man,'" Davis said. "He killed him but you have to understand why. These delusions he has caused the situation."

Jurors rejected defense arguments for a life sentence.

Ward would be the ninth convicted killer in the U.S. to receive lethal injection this year and the fifth in Texas, the nation's most active death penalty state.