The state of Indiana in the United States has carried out its first execution in 15 years, putting to death a man, whose lawyers say he was mentally ill, murdering four people in 1997, including his own brother.

Joseph Corcoran, 49, was executed by lethal injection and pronounced dead early Wednesday morning at the Indiana State Prison in Michigan City, officials said.

His last words were “Not really. Let’s get this over with,” a statement by the Indiana Department of Correction said.

Corcoran’s lawyers argued in court filings that carrying out the death penalty would violate the Constitution because he had long suffered from paranoid schizophrenia, including experiencing hallucinations and delusions, making him unable to understand the severity of his crimes.

Corcoran’s “longstanding and documented mental illness continues to torment him as it did at the time of the 1997 offence,” his legal team said.

His lawyer, Larry Komp, said the question of Corcoran’s mental health was never properly evaluated.

“There has never been a hearing to determine whether he is competent to be executed,” he said in a statement to The Associated Press. “It is an absolute failure for the rule of law to have an execution when the law and proper processes were not followed.”

More than two dozen people were gathered outside the prison before his execution to protest and pray, according to the Indy Star newspaper.

The state provided limited details about the execution process, and no media witnesses were permitted under state law. However, Corcoran chose a reporter for the Indiana Capital Chronicle as one of his witnesses, the outlet’s editor posted on X early Wednesday.

Indiana and Wyoming are the only two states that do not allow members of the media to witness state executions, according to a recent report by the Death Penalty Information Center.

Corcoran was going through a stressful period in July 1997 because the upcoming marriage of his sister meant he would have to move out of the home he was sharing with her and his brother in Fort Wayne, Indiana.

After he overheard his brother, James Corcoran, 30, talking about him, he loaded his rifle and shot his brother and three other men, including his sister’s fiance, according to court filings.

Corcoran had previously been acquitted of the murders of his parents, who were found shot dead in their home in 1992.

“Serves no purpose”

Corcoran’s sister, Kelly Ernst, sought to stop the execution, saying she had forgiven him.

“I believe that the death penalty does not address grief or provide true justice especially for victims, and those with mental illness,” she wrote on December 2 on Facebook.

“Instead, it is a lengthy, costly and political process,” she added. “I believe his execution serves no purpose.”

Corcoran’s execution is the 24th in the United States this year. Indiana paused executions in 2009 because it was unable to obtain the necessary drugs, with pharmaceutical companies reluctant to be associated with capital punishment.

But Indiana Governor Eric Holcomb and Attorney General Todd Rokita, both Republicans, announced earlier this year that the state had acquired the drug – pentobarbital – and that executions would resume, beginning with Corcoran’s.

Corcoran sent a letter last month to the Indiana Supreme Court, saying he no longer wanted to litigate his case.

His lawyers nonetheless filed an emergency appeal to the US Supreme Court on Tuesday to stay the execution, which was ultimately rejected.

“Joseph Corcoran’s case has been reviewed repeatedly over the last 25 years – including 7 times by the Indiana Supreme Court and 3 times by the US Supreme Court, the most recent of which was tonight,” Holcomb said in a news release after the execution was completed.

Rokita also issued a statement, saying Corcoran “finally paid his debt to society as justice was provided to his victims”.

The death penalty has been abolished in 23 of the 50 US states, while six others – Arizona, California, Ohio, Oregon, Pennsylvania and Tennessee – have moratoriums in place.