Matthew E. Farrow pleaded guilty Friday in Orleans County Court to killing his wife April 1 in their Albion home.
Farrow, 46, a disabled Air Force veteran of Operation Desert Storm who uses a wheelchair, pleaded guilty to manslaughter in exchange for a promise that his sentence would not exceed 20 years in prison when it is imposed March 13.
Farrow stabbed his wife, Anne-Marie, 43, in the chest with a 22-inch knife.
He said at the time of his arrest that he believed his wife was having an affair.
She had told him she was kicking him out their Route 31 home the night he killed her.
Investigators said the victim's screams awakened the couple's 10-year-old daughter, who called 911 shortly after 3 a.m.
Police and paramedics rushed to the home -- a one-story house two miles east of the village on Route 31 -- where they said they found Anne-Marie Farrow still alive at about 3:30 a.m.
She died about 45 minutes later in Medina Memorial Hospital.
Orleans County District Attorney Joseph V. Cardone said he agreed to the plea deal for several reasons, including Farrow's illness and a possible defense involving extreme emotional disturbance.
"If you kill someone, obviously that's murder, but the charge could be lowered if it's proved he suffered from extreme emotional disturbance, which basically means a temporary loss of self-control," he said.
Cardone also said he wanted to save the couple's daughter, now 11, from testifying against her father.
The girl had found him over her mother with a blood-covered knife in his hand.
The focus on extreme emotional disturbance may have resulted from another Orleans County case, highlighted earlier this year when an appellate court in Rochester threw out a teenager's guilty plea to fatally shooting his father in 2002.
The slaying of Anne-Marie Farrow was the town's third homicide in the last dozen years.