CLAYTON • In a hearing aimed at negating Scott McLaughlin's death sentence, family members and a DNA expert testified Monday that a relative of his might also be connected to the killing of his ex-girlfriend.

Lawyers for McLaughlin are presenting new evidence in a claim that he did not have effective legal representation when St. Louis County Circuit Judge Steven H. Goldman sentenced him to death.

McLaughlin, of Wright City, was convicted of abducting Beverly Guenther, 45, of Moscow Mills, from her workplace in Earth City and killing her in November 2003. In 2006, jurors found McLaughlin guilty of first-degree murder, rape and armed criminal action in the guilt phase of his trial but could not agree on punishment. Goldman ordered the capital sentence a month later.

On Monday, McLaughlin's cousin, aunt and nephew each testified that they heard another family member admit that he was with McLaughlin during the murder and also raped Guenther's body that night. That relative was never charged in the crime.

Dean Stetler, a professor of molecular biology at the University of Kansas, testified Monday that a DNA expert from the St. Louis County crime laboratory erred when he told jurors at trial that a sample taken from Guenther's body contained only DNA from McLaughlin and the victim.

Stetler said he analyzed the same data and concluded that DNA from this male relative and possibly a fourth unknown person could also be present. He said McLaughlin's DNA is unusually similar to the male relative's; about 69 percent of indicators that DNA experts compare are the same in the two samples, where about 50 percent would be expected.

In their motion, the attorneys argue that the new evidence may mitigate the circumstances that led the judge to order a death sentence.

McLaughlin led police to the body after he was arrested. Police found her blood in his car and his DNA on her body. Days after the murder, McLaughlin even called Guenther's co-workers with an apology, according to testimony at trial.

Guenther had told friends and neighbors that she was afraid of McLaughlin because he stalked her after the couple split in the summer of 2003.

The hearing was set to continue today.