The last words spoken by Billy Ray Irick were, 'I just want to say I'm really sorry,' before he was put to death in a Tennessee state prison on Thursday.

Witnesses to Tennessee’s first execution in nearly a decade say Irick, 59, at first signaled he would have no last words, but then gave a brief statement to those in attendance.

Journalists present reported that the blinds between a witness room and the execution chamber were opened at 7.26pm on Thursday, and about one minute later, Irick was asked if he had any words before the lethal injection drugs began flowing.

Irick was convicted in the 1985 rape and murder of a seven-year-old girl he was babysitting.

At the question of whether he had any final words to say, Irick first appeared to sigh and say 'no.'

But then he said, 'I just want to say I’m really sorry and that... that’s it.'

Irick was convicted of raping and murdering seven-year-old Paula Dyer in 1985.

'What he did to her is the reason he's where he is,' Kathy Jeffers, the other of Paula, told WBIR.

'I am sick of hearing about his pain and his suffering. What about her pain and her suffering? She was 7 years old, raped, sodomized, and strangled to death. I'm sorry, I feel nothing for his pain. Nothing at all. God, forgive me, but I don't.'

Irick was babysitting Paula, along with four of her brothers, the night she was raped, sodomized and strangled to death.

Her brothers were just in the next room and tried to save their sister, but Irick has barricaded the door and they couldn't break through.

He had come to be a trusted member of the large Jeffers family, which included a total of eight children, and had lived with them for more than a year before sexually assaulting and killing Paula.

It was Paula's father, Kenny Jeffers, who found his daughter, lying unconscious with a pool of blood between her legs that night, after Irick had called him home from work right around midnight, saying he couldn't wake her up.

Her father took her to the hospital, and after 45 futile minutes of attempts at lifesaving measures, Paula was pronounced dead.

One minute after he said he was sorry for the horrific events of that night, his eyes closed, and the sounds of snoring and heavy breathing could be heard.

The subtle sounds gave way at 7.34pm to coughing, huffing and deep breaths.

An attendant began yelling 'Billy' and checked the inmate and grabbed his shoulder, but there didn’t seem to be any reaction.

Two minutes later, Irick was not making any noise and began to turn dark purple.

He was pronounced dead at 7.48pm.

Irick is the first death row inmate to be executed by the state of Tennessee since 2009.

The US Supreme Court cleared the way for his execution on Thursday afternoon, denying Irick's final request for a stay.

But Justice Sonia Sotomayor issued a blistering dissent, citing a recent state court trial of a case brought by 33 death row inmates challenging Tennessee's execution drugs.

The state Supreme Court denied Irick a stay on Monday related to those challenges, saying a lawsuit filed by inmates contesting the execution drugs being used wasn't likely to succeed.

Sotomayor wrote that the court is overlooking the potential for 'torturous pain' by that method of execution.

Governor Bill Haslam also had the power to stop his death, but declined to intervene.

In addition to legal challenges, since its last execution in 2009, Tennessee has had difficulties securing execution drugs including its previous chemical of choice, pentobarbital.

But none of those hurdles stopped the process for Irick, who was put to death on Thursday using a combination of midazolam, vecuronium bromid and potassium chloride injections, which stopped his heart.

His final meal consisted of a burger, onion rings and a Pepsi soft drink.

The name of the restaurant that his 'super deluxe combo' meal came from will not be released 'out of an abundance of caution,' according to Tennessee Department of Correction spokeswoman.

Death row inmates are limited to $20 for their last meal, according to The Tennessean.

Irick, 59, was moved to death watch earlier this week, meaning he was being held in an 8-foot-by-10-foot cell in sight of the death chamber with strictly regulated visitation rights.

Irick was first set to be executed on May 4, 1987.

His attorneys have filed a series of appeals over the past several decades, with claims of insanity and the unconstitutional use of the electric chair as a back-up to lethal injection.

In July Irick's attorney asked for the Tennessee Supreme Court to delay his execution once again amid a challenge to the state's lethal injection protocol.

For the first time, Tennessee used midazolam as a sedative, the muscle relaxer vecuronium bromid, and then potassium chloride to stop the heart.

At question is whether midazolam is effective in rendering someone unconscious and unable to feel pain from the other two drugs.

But Tennessee Supreme Court judges ruled Irick's attorney had failed to demonstrate a substantially less painful means to carry out the execution or that the drugs the state plans to use would cause the inmate to be tortured to death.

Federal public defender Kelley Henry had requested the US Supreme Court to delay his execution.

The Supreme Court rarely stays executions.

Henry had asked Haslam to issue a temporary reprieve while the drugs are studied further.

But the governor quickly ruled it out, saying he would not intervene.

'My role is not to be the 13th juror or the judge or to impose my personal views, but to carefully review the judicial process to make sure it was full and fair,' Henry said.

'Because of the extremely thorough judicial review of all of the evidence and arguments at every stage in this case, clemency is not appropriate.'

During the last trial, Henry cited witnesses that described some inmates who still could move, shed a tear, gasp and gulp 'like a fish out of water' while being put to death.

'Today's decision means that Mr Irick faces a scheduled execution date before the courts have had a chance to thoughtfully consider the challenge to the new lethal injection protocol,' Henry said in a statement on Monday.

In a dissenting opinion, Justice Sharon Lee added that she 'will not join in the rush to execute Mr Irick and would instead grant him a stay to prevent ending his life before his appeal can be adjudicated.'

Attorneys for the state have said the US Supreme Court has upheld the use of midazolam in a three-drug series.

Paula's mother, Kathy Jeffers, said she has no sympathy for Irick.

'What he did to her is the reason he's where he is,' she told WBIR-TV.

'I am sick of hearing about his pain and his suffering. What about her pain and her suffering?'

'She was seven years old, raped, sodomized, and strangled to death. I'm sorry, I feel nothing for his pain. Nothing at all. God, forgive me, but I don't.'