The state of Indiana intends to carry out its first execution in 15 years before sunrise Wednesday, though attorneys for the condemned inmate are fighting to halt the lethal injection, citing his mental illness.

Lawyers for Joseph Corcoran – sentenced to die for the 1997 murders of four men, including his brother and his sister’s fiance – have argued in court filings that putting him to death would violate the Eighth and Fourteenth Amendments because he has long suffered from paranoid schizophrenia.

The 49-year-old experiences auditory hallucinations and delusions, falsely believing prison guards have been torturing him using sound waves, they note. Corcoran does not have a rational understanding of his situation, they argue, despite the inmate’s own written statements indicating he wants his execution to proceed.

Neither the Indiana Supreme Court nor a judge from the US District Court in northern Indiana have been convinced by the attorneys’ arguments, and the courts have so far declined to halt the execution. Corcoran was convicted of murdering his brother, James Corcoran; his sister’s fiancé, Robert Scott Turner; as well as Timothy Bricker and Douglas Stillwell.

The scheduled execution comes about six months after GOP Gov. Eric Holcomb announced the state had, “(a)fter years of effort,” obtained the drug pentobarbital, allowing the state to resume capital punishment for the first time since 2009.

A number of jurisdictions have relied on the sedative to carry out lethal injections in recent years, as states struggle to obtain the drugs they previously used. Pharmaceutical companies opposed to capital punishment have prohibited the use of their products for executions.

“Accordingly, I am fulfilling my duties as governor to follow the law and move forward appropriately in this matter,” Gov. Holcomb said in a statement this summer.

Indiana Attorney General Todd Rokita cast the death penalty “as a means of providing justice for victims of society’s most heinous crimes and holding perpetrators accountable.”

“Now that the Indiana Department of Correction is prepared to carry out the lawfully imposed sentence,” Rokita said, “it’s incumbent on our justice system to immediately enable executions in our prisons to resume.”

Killer’s sister opposes the execution

Corcoran’s sister, Kelly Ernst – who was also a sister to victim James Corcoran and engaged to Turner – opposes her brother’s execution and the death penalty more broadly, telling the Associated Press she believes Corcoran’s serious mental illness is “fairly obvious.”

“I kind of just feel that there’s no such thing as closure,” Ernst, 56, told the AP. “I just don’t know what else to say. I haven’t slept in weeks.”

CNN has reached out to Ernst for comment.

Adam Bricker, the brother of victim Timothy Bricker, told CNN he doesn’t feel strongly about whether Corcoran is executed or spends the rest of his life in prison. But he wants the matter to be brought to a conclusion after enduring so many years of intermittent news coverage about the case, which reawakens his family’s pain.

“It’s not fair to my mom, his kids that are still living, everybody. It’s not fair and it’s not cool,” Adam Bricker said.

“As a Christian, I don’t wish anybody to die,” he added. “I didn’t wish my brother to die either. But I think the laws need to be followed.”

Indiana is one of just two states with the death penalty that does not allow news reporters to witness an execution, according to the Death Penalty Information Center. State law indicates those present may include corrections officials, the condemned’s spiritual advisor, up to five friends or relatives of the inmate and up to eight members of the victim’s or victims’ immediate families.

In other states, media witnesses generally act as neutral public monitors, reporting details of an execution to the public. That can occasionally mean reporting accounts of executions that ran afoul of a state’s protocol – a particularly important responsibility when they contradict officials’ characterization of events.

A history of mental illness

At the time of the killings, Corcoran was stressed because his sister’s upcoming marriage would have required he move out of her house, according to a summary of the case included in the Indiana Supreme Court’s ruling this month. Corcoran – who the AP reported had been charged but acquitted in the murders of his parents in 1992 – woke up one afternoon and purportedly heard his brother and the other men talking about him, that summary says, and he fatally shot all four with a rifle.

Evidence of Corcoran’s mental illness predate the murders, his attorneys said in an appeal in federal court his month, citing witnesses who recalled him speaking to people who were not present or instances where he wrongly insisted people were talking about him.

Corcoran’s attorneys maintain he should never have stood trial. But his two lawyers at the time did not realize the extent of his mental illness, they wrote in new affidavits, and they did not request a competency hearing.

When his attorneys attempted to file a post-conviction appeal, Corcoran at first refused to sign it, a decision that at the time prevented its review. His attorneys argued in a 2003 hearing that Corcoran was incompetent, and they presented testimony by three mental health experts, each of whom diagnosed Corcoran with paranoid schizophrenia.

The court ultimately found Corcoran was competent to waive his appeals, and while the inmate would later change his mind, it was too late. His petition was dismissed.

Corcoran’s illness has not improved in the last two decades, and it’s proven resistant to the Indiana Department of Corrections’ attempts at medication, his attorneys say.

Still, the state supreme court this month ruled his attorneys had failed to prove that anything has changed since the inmate was deemed competent. A federal judge similarly determined the claim that Corcoran was incompetent for execution was without merit.

Both courts pointed in part to a recent affidavit submitted to the state’s high court, in which Corcoran wrote he wanted to abandon his appeals and claimed he understood the consequences of being executed. But Corcoran’s attorneys argued this affidavit was not credible, citing another psychiatrist who determined the inmate’s writings – while appearing logical – are tied to his delusions.

“It is unreasonable to allow the insane to determine their own competency,” the attorneys wrote.