The planned execution of an Arizona man remains on track after two last-minute court efforts ended without decisions that would sidetrack the state from putting 66-year-old Clarence Dixon to death.

Early on Monday, the state supreme court declined to overturn a lower court ruling that found Dixon is competent to be put to death.

Later, Dixon’s lawyers dropped a federal court challenge against the drug the state planned to use after agreeing that a new batch mixed by a pharmacist negated their argument that the drugs had expired.

Dixon is set to be executed at the state prison in Florence on Wednesday morning, a move that will end decades of waiting for the family of the 21-year-old Arizona State University student he killed in 1978.

Leslie James, the older sister of the victim, Deana Bowdoin, was in federal court on Monday morning as the proceedings unfolded and plans to be at the prison on Wednesday.

Because of the ongoing legal wrangling over the case, she declined to comment through her lawyer.

In the state supreme court action, the high court without comment declined to review last week’s decision from a judge in Pinal County that rejected arguments that mental illness made Dixon unable to understand why he was being put to death.

While the judge found Dixon suffers from schizophrenia, he said he is rational and understands the proceedings in his case well enough to show he is competent.

Dixon’s lawyers are now expected to ask a federal judge in Phoenix to consider whether his mental illness means it would be unconstitutional to execute him.

That had not been filed by Monday evening.

Dixon’s lawyers had challenged the state’s planned use of a batch of the sedative sodium pentobarbital that was mixed in February, contending it has expired and using it would violate Arizona’s execution rules.

Lawyers for Arizona denied that the drug has expired but offered to mix up the new batch and have it tested for potency.

Because it will be used within three days, there is no concern it will be out of date.

Whether the expired drug challenge claim would have been successful was in doubt.

At a Monday morning hearing to consider that claim, US district court judge Diane Humetewa said she “struggled” to see how the argument raised a valid constitutional issue in light of US supreme court rulings that said courts should not meddle in the details of state lethal injection decisions.

“The question that I struggle with is: does that rise to a constitutional right?” she asked Dixon lawyer Jennifer Moreno.

Ms Moreno told the judge that a 2017 settlement agreement required Arizona to use non-expired drugs, and that helps build their claim that using expired pentobarbital would equate to cruel and unusual punishment.

“Without a proper test, those drugs should have been disposed of and we shouldn’t even be talking about this,” Ms Moreno said.

But she acknowledged that if the state is able to mix the new batch and get it tested before the scheduled 10am on Wednesday execution, “that resolves the outstanding issues in this case”.

That happened on Monday evening, when Ms Humetewa called the court back into session and Ms Moreno and assistant Arizona attorney general Jeff Sparks told her they had agreed that using a new batch would end the litigation.

Arizona and many other states have struggled to get execution drugs in recent years after drug-makers refused to sell their products for that use.

Arizona obtained the pentobarbital it plans to use from an unidentified compounding pharmacy.

Dixon, who is blind and in declining health, is set to be the first person put to death in Arizona in nearly eight years, mainly because of problems with the last execution.

The state had to give Joseph Wood 15 doses of a two-drug combination over two hours before he died in July 2014 in an execution that his lawyers said was botched.

The state is now using just one drug.

Dixon was serving life sentences for a 1985 attack on a 21-year-old Northern Arizona University student when DNA testing linked him to Ms Bowdoin’s unsolved rape and murder.

Dixon had been found “not guilty by reason of insanity” in a 1977 assault case in which the verdict was delivered by then-Maricopa County superior court judge Sandra Day O’Connor, nearly four years before her appointment to the US supreme court.

Ms Bowdoin was killed on January 7 1978, two days after that verdict, according to court records.

She was found dead in her apartment and had been raped, stabbed and strangled.

Dixon was also charged with raping Ms Bowdoin, but the charge was later dropped on statute-of-limitation grounds.

He was convicted, though, over her death.

Defence lawyers said Dixon has been diagnosed with paranoid schizophrenia on multiple occasions, has regularly experienced hallucinations over the past 30 years and should not be executed.

Last Tuesday, the Arizona supreme court issued a warrant for a second execution.

Frank Atwood is set to die on June 8 for killing an eight-year-old girl in 1984.

Authorities say Atwood kidnapped the girl, whose body was found in the desert north-west of Tucson.