Ohio could regain its status as one of America's busiest death penalty states, with 11 executions scheduled over the next 20 months.

This follows the resumption of lethal injection in the case of a man who fatally stabbed the 15-year-old son of his former employers.

Wrangling over the state's execution procedures has delayed the imposition of capital punishment since last July, but a US federal judge has cleared the state to proceed.

Yesterday, Mark Wiles died by lethal injection at 10.42am local time, with the inmate using his final words to express hope that his death would bring closure to his victim's family, but also protesting against the death penalty.

Wiles concluded, reading a statement that the warden held over his head: "Finally, the state of Ohio should not be in the business of killing its citizens. May God bless us all that fall short."

It was the 47th execution since Ohio resumed putting inmates to death in 1999, and the state has 11 more executions scheduled, including in June, July, September and November.

The next scheduled execution is on June 6, when condemned killer Abdul Awkal, 52, is set to die for killing his estranged wife and brother-in-law in 1992 in a room in Cuyahoga county domestic relations court.

Wiles, looking haggard with a sparse, cropped grey beard and shaven head, stared at witnesses for a few moments when he entered the death chamber. A few minutes later, strapped to a gurney and with intravenous lines inserted into his arms, he raised his head and looked at witnesses again.

"Since this needs to be happening, truly I pray that my dying brings some solace and closure to the Klima family and their loved ones," he said.

Wiles, 49, also thanked his family for their love and support.

As the lethal sedative began flowing, Wiles nodded, appeared to be speaking, swallowed, spoke again, then gasped a few moments later.

His stomach rose and fell several times and his head moved slightly, then his mouth fell open and he lay still for several minutes before he was pronounced dead.

John Craig, a cousin of Wiles's victim Mark Klima and a witness of the execution, appeared briefly before reporters to respond to the prisoner's last words.

"It's my opinion that Mark Wiles gave up his citizenship to Ohio when he murdered my cousin and became an inmate, more or less a condemned man," Mr Craig said.

Wiles, who dropped his final appeal last week, told the Ohio Parole Board that he was not sure he deserved mercy but he was requesting clemency because he had to. Both the parole board and governor John Kasich denied Wiles's request.

Wiles's defence team had argued he should be spared because he confessed to the crime, showed remorse and had a good prison record.

Wiles was not "the worst of the worst", and the parole board showed inconsistency in allowing his execution, his public defenders said in a statement.

Records show that Wiles surprised 15-year-old Mark Klima during a burglary at his family's farmhouse and stabbed him repeatedly with a kitchen knife until he stopped moving.

Wiles paced back and forth and was emotional and anxious in his last minutes in his cell, a few steps from the death chamber, prisons spokeswoman JoEllen Smith said.

The inmate spent the night on the phone, listening to the radio and writing letters.

He and two sisters and a brother-in-law cried during emotional visits yesterday morning, and he also said the rosary with his spiritual adviser, a Roman Catholic priest who works at Ohio's death row in Chillicothe.

Wiles did not sleep after arriving at the death house on Tuesday morning at about 9.45am.

Ohio's recent execution delays stem from inmates' lawsuits over how well executioners perform their duties.

The state has a review process in place that allows prisons director Gary Mohr to oversee the details and procedures of the execution policy.

Before the execution, Mr Mohr said he was "absolutely confident" in the state's ability to carry out the procedure properly.

"We have more documentation on this than anything in my 38 years that I've been in this business," Mr Mohr said. "It's the most documented execution in the United States of America."