COEUR D'ALENE, Idaho (AP) - The lawyer defending Joseph Duncan III, accused of killing three people, has asked for details on Idaho's method of execution in what could be a first step in challenging its constitutionality.

Public defender John Adams earlier this week requested the state's protocol on the method of execution from prosecutors. He wants to know what drugs the state would use during lethal injection and how they would be administered.

"The prosecutor says that if they get a conviction they're going to seek a sentence of death," Adams told The Spokesman-Review. "There's a question of whether Idaho has a protocol that's constitutionally acceptable for executing prisoners. We want to know the protocol so we can address that."

Duncan has pleaded not guilty to three counts of first-degree murder and three counts of first-degree kidnapping in the May 16, 2005, slayings of Brenda Kay Groene, 40; her son, Slade Vincent Groene, 13; and Mark Edward McKenzie, 37, at their Coeur d'Alene-area home.

Taken from the home were Brenda Groene's children, 9-year-old Dylan Groene and 8-year-old Shasta Groene. Shasta was recovered when Duncan was arrested at a Coeur d'Alene restaurant on July 2, 2005, while Dylan's body was subsequently found at a Montana campsite.

Federal prosecutors say that when the state case is resolved, federal charges will be filed in the children's abductions and Dylan's death.

Duncan spent most of his adult life in prisons in Washington state for the sexual abuse of children. Before his arrest in the Groene case, he had lived in Fargo, N.D., where he was a computer science student at North Dakota State University.

Mark Vovos, a defense attorney in Spokane, said some questions surrounding executions are whether the person being executed would be given anesthesia, whether the person would feel pain, and whether the person would be able to let someone know they were in pain.

"Any attorney who would be death-qualified is going to challenge every aspect of the death penalty law, and he has an obligation to do that," Vovos said.

Besides lethal injection, Idaho allows execution by firing squad when lethal injection is considered "impractical." Since 1864, 27 people have been executed in Idaho, the last in 1994.