KANSAS CITY, Mo. — Lorenzo Gilyard, a former trash company supervisor described by neighbors as mild-mannered and friendly, went on trial Monday in the serial killings of woman and girls in the Kansas City area, most of them prostitutes.

Gilyard was charged with 13 killings between 1977 and 1993, but he faces only seven counts in this trial.

If convicted on even one count of first-degree murder, his only possible sentence would be life without parole. Prosecutors agreed in January not seek the death penalty as long as Gilyard’s attorneys agreed to a trial before a judge without a jury. His attorneys also agreed to give up nearly all of their client’s appeal rights.

Gilyard, 56, was jailed in 2004 in connection with the strangulation of 12 of the victims. Authorities added the 13th murder charge last year — a 26-year-old woman found dead on a street in 1989 with a paper towel in her mouth and strangulation marks around her neck.

The trial will revolve largely around DNA evidence — without which the murder cases might have continued to languish without a suspect.

In telephone conversations with his relatives, Gilyard has consistently contended he is innocent and eager to go to trial.

“I know I couldn’t get convicted of something I didn’t do,” Gilyard told a relative in one call, among more than 200 minutes of recordings The Kansas City Star recently obtained through a Missouri Sunshine Law request.

Gilyard rarely discussed details of his case, but in one conversation he talked about the DNA evidence that prosecutors say linked him to the victims. He told a friend his trial would come down to “their scientists against my scientists.”

Gilyard had a long history of scrapes with the law and served time for crimes including child molestation. State probation records show that from January 1969 to June 1974, he was a suspect in five rape cases, though he was never convicted.

But Gilyard had been largely off the police radar in the years before his April 2004 arrest.

By then, Gilyard lived with his wife of about a decade in a modest home at the end of a quiet dead-end street in south Kansas City. His wife divorced him after his arrest.

A crime lab eventually used DNA to link 13 killings to a single suspect. The identify of that suspect remained unknown until the lab analyzed a blood sample taken from Gilyard in 1987, when he was a suspect in the death of one of the women he is now charged with killing.

Court papers filed by the defense list the victims as Catherine M. Barry, 34; Naomi Kelly, 23; Ann Barnes, 36; Kellie A. Ford, 20; Angela Mayhew, 19; Sheila Ingold, 36; and Carmeline Hibbs, 30.

The other victims were identified as Stacie L. Swofford, 17; Gwendolyn Kizine, 15; Margaret J. Miller, 17; Debbie Blevins, 32; Helga Kruger, 26; and Connie Luther, 29.

The trial is expected to last three weeks. Prosecutors have said Gilyard could face trial later on the other six murder counts if necessary.