(CNN) -- Nearly 35 years after a Texas judge sentenced him to death, Ronald Chambers was found dead Monday morning on the floor of his cell.
Guards found Chambers, 55, unresponsive around 6:30 a.m. while doing their rounds, Dallas County Sheriff Spokeswoman Kim Leach said. He was then transported to Parkland Memorial Hospital in Dallas, where he was pronounced dead.
The Dallas County medical examiner's office said it would take six to 12 weeks before Chambers' cause of death could be definitively determined. But Leach said Chambers had many health complications when he came last year to the Dallas County jail.
Chambers was 19 when he and Clarence Ray Williams kidnapped Mike McMahon and his date from the parking lot of a Dallas nightclub, then ordered them down the embankment of the Trinity River, according to the Texas Attorney General's Office. The two men robbed the couple and, after shooting at them, left them for dead.
The female survivor, Deia Sutton, testified that she and her boyfriend survived the first attack, but Chambers went back and killed McMahan by repeatedly hitting him over the head with the barrel of a shotgun.
On December 18, 1975, a jury found Chambers guilty of capital murder and a judge subsequently put him on the state's death row.
The Texas Court of Criminal Appeals twice set aside his conviction -- once because he wasn't read his Miranda rights after being interviewed by a state psychiatrist -- but both times he was retried and convicted again.
In 2007, the U.S. Supreme Court again granted Chambers a stay of execution, amid questions about the instructions given to the jury, the Dallas Observer reported. The case was sent back to Texas and a fourth sentencing trial was set for spring 2011, according to published reports.
While numerous reports called Chambers the "Dean of Death Row," because of the various legal maneuverings he didn't have a death sentence the entire time he was behind bars, including at the time of his death. Excell White, who killed four people in 1974 and wasn't executed until 1999, spent more time -- 8,854 days -- on death row before being put to death than any other Texas convict.
Texas, which has executed more prisoners since 1976 than any other state, pays $86.08 to execute a death row inmate, or the cost of drugs used in a lethal injection, the state's Division of Criminal Justice reports. That compares to the $17,338, on average, that it costs to jail a Texas inmate for 12 months, according to 2009 data from the National Institute of Corrections, which is below the national yearly average of $28,689.