"This is not a whodunnit," attorney Tawni Hanseen told a 3rd District Court jury during her opening statement.
But Hanseen said Walker was "suicidal not homicidal" on the day of the shooting, which was punctuated by a series of telephone arguments with his wife, Cassandra Bryan, and a personal confrontation at the George E. Wahlen Veterans Administration Medical Center, where she worked as a nurse.
Hanseen said Walker "got drunk, took pills and got a gun out - prepared to take his own life."
But when a "furious" Bryan came home from work early and attacked Walker, he used the gun to defend himself, she said.
"He killed her," Hanseen said, "But he is not the monster the prosecution will say he is."
Walker, 57, is charged with first-degree felony murder for the April 1, 2006, slaying of his 46-year-old wife. But evidence of diminished mental capacity could result in a lesser verdict of manslaughter, and a finding of self-defense could exonerate Walker.
But Salt Lake County District Attorney Robert Neill noted that Bryan bled to death from 33 gunshot wounds, including a final shot into her head as she lay face-down on their kitchen floor.
And after the shooting, Walker told detectives, "I don't want her leaving me," Neill said.
Prosecutors believe Walker used a samurai sword found at the scene to cut himself above his right eye. The defense has said there is no evidence the wound was self-inflicted.
The prosecutor said Bryan had decided earlier that day to divorce her husband, who did not work and whom she pampered with purchases of televisions, golf clubs, a Harley-Davidson motorcycle and a Mercedes-Benz automobile.
According to testimony from other nurses, Bryan removed her wedding ring after an angry Walker came to the hospital to see her.
"She said she hated him and wanted to divorce him," testified co-worker Janet Beverly.
Co-worker Brenda Devitt testified that Bryan told her Walker had "cleaned out" her bank account.
Co-worker Nancy Greene said Bryan was "very pampering toward [Walker's] needs and considerate of his desires. Anything he requested, she took seriously."
But Greene said that following a hysterectomy in January 2006, Bryan experienced hormonal changes that allowed her to see her relationship in a new light.
"She said it was like a veil was taken off," Greene said.
As Beverly put it, "She was not as patient with Steve when he acted like a child."
Walker and Bryan got married about 10 years ago, just two days after meeting at the VA hospital, where Walker was a patient.
Hanseen said that because of the "scary, horrible things" Walker saw as a helicopter gunner in Vietnam, he suffered flashbacks, nightmares and had a hair-trigger startle reflex.
She said Walker's condition made him unable to work and the government had declared him 100 percent disabled.
Walker was "always on alert" for an enemy attack, she said. "At night he would patrol the house."
But she said Bryan, who was able to see past Walker's problems, helped him stop drinking and persuaded him to try counseling.
"But there was a dark side," Hanseen said. "They had their problems."
Hanseen said Bryan had something she called a "husband stick," which she initially used to wake Walker and avoid his startle response, but later used to hit him.
Co-worker Greene said Bryan was never violent.
But during cross-examination, Greene said Bryan had told her that if Walker ever "did anything to her," she would kill him.
