LUCASVILLE, Ohio – A condemned man appeared to gasp several times and took an unusually long time to die — more than 20 minutes — in an execution carried out Thursday with a combination of drugs never before tried in the U.S.

Dennis McGuire's attorney Allen Bohnert called the convicted killer's death "a failed, agonizing experiment" and added: "The people of the state of Ohio should be appalled at what was done here today in their names."

McGuire's lawyers had attempted last week to block his execution, arguing that the untried method could cause him to suffer "agony and terror" while struggling to catch his breath.

McGuire, 53, made loud snorting noises during one of the longest executions since Ohio resumed capital punishment in 1999. Nearly 25 minutes passed between the time the lethal drugs began flowing and McGuire was pronounced dead at 10:53 a.m.

Executions under the old method were typically much shorter and did not cause the kind of sounds McGuire made.

Ohio prisons spokeswoman JoEllen Smith had no comment on how the execution went but said a review will be conducted as usual.

Prison officials gave intravenous doses of two drugs, the sedative midazolam and the painkiller hydromorphone, to put McGuire to death for the 1989 rape and fatal stabbing of Joy Stewart.

The method was adopted after supplies of a previously used drug dried up because the manufacturer declared it off limits for capital punishment.

The execution is certain to launch a new round of federal lawsuits over Ohio's injection procedure. The state has five more executions scheduled this year, with the next on Feb. 19.

What was particularly unusual Thursday was the five minutes or so that McGuire lay motionless on the gurney after the drugs began flowing, followed by a sudden snort and then more than 10 minutes of irregular breathing and gasping.

"Oh, my God," his daughter, Amber McGuire, said as she watched her father's final moments.

In pressing for the execution to go ahead, Assistant Ohio Attorney General Thomas Madden had argued that while the U.S. Constitution bans cruel and unusual punishment, "you're not entitled to a pain-free execution."