JONESBORO, Ill. -- A judge resentenced convicted murderer Mark Gibbs to life in prison Friday for killing his parents after Gibbs told the court he was "sorry for what I have done."

Gibbs, 45, told Judge Jeff Farris, "My parents did not deserve to die."

Gibbs said killing his parents was his "worst mistake."

The defense had portrayed Gibbs as a victim of abuse at the hand of his father, who was described as a violent drunk.

But Farris said Gibbs not only killed his father, but shot his mother twice and failed to call for medical help as his mother lay drowning in her own blood in the family home.

Gibbs showed little emotion throughout the hearing, a fact which Farris commented on during the sentencing. He described the defendant as being "cool" in the courtroom.

Members of the Gibbs family welcomed the ruling.

After the judge handed down the sentence, Bradley Pender, a first cousin of Mark Gibbs, said he felt justice was served. Pender and many other relatives spent hours in court during the two days of hearings. "We are ready to get on with our normal lives," he said. "We are just glad it is over."

Relatives of the father had urged the judge to keep Gibbs in prison. Three relatives of the mother had argued Gibbs be released.

Gibbs was 17 when he shot his parents in their rural home near Reynoldsville, Illinois, in Union County on Jan. 6, 1992.

His father, Richard Gibbs, died at the scene from a single gunshot wound to the head. His mother, Betty Gibbs, was shot twice in the head with the same .22-caliber pistol, which was later found in a creek.

Betty Gibbs was transported to Southeast Hospital in Cape Girardeau where she died days later.

Mark Gibbs received a mandatory sentence of life in prison.

He has spent nearly three decades behind bars. Gibbs pleaded guilty to the crimes in 1995 and since then has been incarcerated in the state prison system. He is being held at the maximum security prison in Pontiac, Illinois.

The resentencing was prompted by later court rulings.

The U.S. Supreme Court in a 5-4 decision in 2012 found mandatory life sentences for juveniles without the possibility of parole are unconstitutional.

The high court said such punishment violates the Eighth Amendment's prohibition against cruel and unusual punishment.

Two years later, the Illinois Supreme Court unanimously held the U.S. Supreme Court's decision applied retroactively to sentences imposed before 2012.

The defense team, led by attorney J. Damian Ortiz, argued Gibbs violent actions were in response to years of domestic violence in the home, and urged the judge hand down a lesser sentence.

But state appellate prosecutor David Robinson said there was no evidence of abuse. There were no police reports, school records or photographs showing any signs of abuse, he told the judge.

Robinson said Gibbs planned the murders in a "cold, calculated way."

Farris said testimony showed Mark Gibbs told fellow students he planned to kill his parents.

Richard Gibbs was asleep on the floor and Betty Gibbs was asleep on the couch of their rural Union County home when they were shot at close range, Farris said.

The judge said he doesn't know whether there was any domestic abuse, but he said, "I can't get past the mother."

Farris said Gibbs knew his mother was still alive, but instead of seeking medical help for her, he took money from his father's wallet and drove to a grocery store. He also threw the gun in a creek, the judge said.

Only later did he return home and call his uncle, Gary Gibbs, to report his parents had been shot, the judge said.

Farris said Gibbs drove a vehicle and could have left home without killing his parents. "Why didn't he run away before the trigger was pulled?" asked Farris.

The sentencing came after a hearing, which extended over two days. The hearing began Nov. 15 in the Union County Courthouse. It resumed Friday morning, with the judge issuing his ruling Friday afternoon.

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