Durham, N.C. — A lawyer for Durham novelist and one-time mayoral candidate Mike Peterson resumed his attack Tuesday on the competency of a key prosecution witness in Peterson's 2003 murder trial.

Peterson was convicted of first-degree murder in the Dec. 9, 2001, beating death of his wife. Kathleen Peterson was found dead in a pool of blood at the bottom of a staircase in the couple's upscale Durham home.

He is seeking a new trial, arguing that former State Bureau of Investigation analyst Duane Deaver provided misleading testimony about blood evidence.

Defense attorney David Rudolf spent much of last week trying to discredit Deaver, whom the SBI fired in January. An agency official said Deaver was known to be biased in favor of prosecutors, and blood evidence experts said the tests he conducted in the Peterson case were flawed.

On Tuesday, another blood evidence expert questioned Deaver's expertise and his calculations.

Thomas Bevel, president of Bevel, Gardner & Associates, an Oklahoma-based forensic science consulting company, noted that Deaver hasn't taken any professional training courses in more than 20 years and doesn't belong to any professional organizations, which would provide some peer review of his work.

Deaver's work in the Peterson case was "not scientifically sound," Bevel testified, saying Deaver didn't document details of blood spatter found in the stairwell properly and used incorrect measurements.

At one point in the hearing, Bevel even banged his head against a wall in the courtroom to demonstrate how Kathleen Peterson could have been injured other than being killed.

Durham County District Attorney Tracey Cline challenged Bevel's conclusions, saying he hasn't reviewed some of the evidence from the trial.

"Could you give a conclusion as to whether (Deaver) was right or wrong?" Cline asked him.

Bevel never answered the question directly.

"There are numerous areas here where I disagree," he said.

Ronald Guerette, a Charlotte private investigator who reviewed all of Deaver's case files at the SBI, said Deaver rarely conducted forensic experiments on blood evidence and hadn't visited a crime scene in more than four years before going to the Peterson home.

Cline is expected to present witnesses Wednesday to back up her case that there was nothing wrong with Deaver's testimony and that Peterson shouldn't receive a new trial.