ERIE — Expert witnesses disagreed Wednesday over whether a woman was mentally fit to stand trial on charges that she helped plot an elaborate bank robbery that ended with the death of a pizza deliveryman who was wearing a time bomb around his neck.

Dr. Robert Sadoff, a professor of psychiatry at the University of Pennsylvania, testified at a competency hearing that Marjorie Diehl-Armstrong "absolutely" has bipolar disorder and that the condition interferes with her ability to deal with her court-appointed lawyer.

"It's clear to me she has and has had bipolar disorder for a number of years," Sadoff, who said he evaluated Diehl-Armstrong and has known her since the 1980s, told defense attorney Thomas Patton. "She is not able to rationally assist you in preparing a defense."

Diehl-Armstrong, 59, and Kenneth Barnes were indicted in July on bank robbery, conspiracy and a firearms violation in the August 2003 robbery that left pizza deliveryman Brian Wells dead.

Wells, 46, told police he was forced at gunpoint to wear a bomb around his neck and rob the PNC Bank outside Erie. As officers waited for a bomb squad, the device exploded, killing him. Wells was named as an unindicted coconspirator, but his family says he was innocent.

Sadoff's testimony countered earlier testimony by Dr. William J. Ryan, a forensic psychologist with the federal Bureau of Prisons.

Ryan said that Diehl-Armstrong does not have bipolar disorder and is competent to stand trial.