The search warrant said inmate Byron Scherf, 52, acknowledged the crime to detectives Wednesday in a videotaped interview, The Herald newspaper of Everett reported.
"I'll just get right to the point. I'm responsible for the death of the correctional officer at the Monroe, uh, correctional facility," he said, according to excerpts cited in the court papers. "I strangled her to death on Jan. 29 at approximately 8:40 p.m. in the chapel."
The interview came after Scherf asked detectives for a chance to tell them what happened, according to the warrant, which said he acknowledged his right to remain silent, then confessed.
Scherf's public defender, Bill Jaquette, did not immediately return a call Friday seeking comment.
Scherf reportedly told detectives he was angry at Biendl over how she had spoken with him at about 8:15 to 8:25 while he worked in the prison chapel that evening.
As he thought about it more, "I got to the point where I knew I was going to kill her," he reportedly said.
According to the search warrant, Biendl sent the inmates back to their cells at about 8:30 and began closing the chapel.
Scherf said he decided to hang back and attacked Biendl from behind, it said. He detailed a struggle that lasted about four minutes, with Biendl trying, and apparently failing, to radio for help, in part because he disabled her communications equipment, according to the document.
Scherf said Biendl bit and scratched him and stomped on his foot trying to get free. They wound up on the ground and he used a cable from an amplifier to fatally choke her, he reportedly told detectives.
He was described as becoming emotional as he said, "I'm certainly sorry."
Scherf since 1997 has been serving life in prison without possibility of release after being convicted of three attacks on women.
The search warrant was obtained to look for trace evidence that would be expected to have been left behind inside the chapel if the fight happened as Scherf described.
The warrant is one of several made public in the last few days. One released Thursday said Scherf had asked others who attended the chapel to pray for him two days before the killing because he was struggling with temptation.
He volunteered at the chapel where he worked as a janitor and clerk. He's jailed in Everett for the homicide investigation.
The search warrants make clear that detectives are preparing for a possible death penalty case.
The search warrants show investigators have been spending considerable time with Scherf since the killing. For example, they obtained a judge's permission to carefully photograph Scherf's nude body under special lights that make it easier to spot injuries, including hidden bruises.
Information from: The Daily Herald, http://www.heraldnet.com