Kansas City, Mo. ? A former trash company supervisor who has been called Missouri’s most prolific serial killer pleaded not guilty Tuesday to a 13th slaying.

Last week Lorenzo J. Gilyard, 55, was charged with first-degree murder in the death of Helga Kruger, an Austrian national who was found in February 1989 lying facedown in a street.

The handcuffed Gilyard, wearing an orange jumpsuit, was arraigned during Tuesday’s brief appearance in Jackson County Circuit Court. Judge K. Preston Dean set Gilyard’s next court appearance for July 17.

Gilyard already had pleaded not guilty to earlier charges of strangling a dozen women – all but one a prostitute – between 1977 and 1993. Gilyard was arrested in April 2004 after a crime lab matched DNA left on the victims to his blood sample. Prosecutor Mike Sanders said Gilyard’s trial on those slayings would be in October.

He said Kruger’s slaying would be tried separately to avoid slowing the prosecution. Gilyard is being held without bond at the Jackson County Jail.

The crime lab linked DNA from Kruger to Gilyard in February.

Sanders has said Kruger moved to Kansas City in 1987, after leaving her native Innsbruck, Austria, a few years earlier. But detectives have been unable in recent months to find anyone who knew her, and prosecutors have offered few details about her past. Sanders has declined to discuss whether Kruger was a prostitute, but court records show she was convicted of solicitation in 1988 and 1989.

Gilyard’s public defender, Tom Jacquinot, said he didn’t think Gilyard even knew Kruger. “We’re in the dark about who Miss Kruger is and where she came from,” Jacquinot said.

Gilyard was married when he was charged with the killings, and Jacquinot said his client led “a very normal, everyday life.”

While some neighbors have described him as mild-mannered and friendly, the suspect had a long history of scrapes with the law, and police had taken a blood sample from him in 1987.