Updated

A woman accused of planning a bizarre bank robbery that ended with a pizza deliveryman dead after a bomb locked around his neck exploded pleaded not guilty Tuesday to robbery, conspiracy and a firearms charge.

Marjorie Diehl-Armstrong's public defender, Thomas Patton, entered the plea on her behalf and said she understands the charges filed against her last week.

Diehl-Armstrong was not at the federal court hearing because Patton said he worried that her bipolar disorder and manic behavior would lead her to talk to investigators on the long drive from Muncy prison, where she is serving seven to 20 years for killing her boyfriend.

Federal prosecutors on Wednesday charged Diehl-Armstrong, 58, and Kenneth E. Barnes, 53, with bank robbery, conspiracy and a firearms violation in connection with the Aug. 28, 2003, robbery of a PNC Bank in Summit Township near Erie.

Pizza deliveryman Brian Wells, 46, told police he had been forced at gunpoint to wear a time bomb around his neck and rob the bank. The device exploded, killing him, while officers waited for the bomb squad to arrive.

Prosecutors accused Diehl-Armstrong of planning the heist to get money to hire someone to kill her father. Barnes, already jailed on unrelated drug charges, pleaded not guilty last week.

Prosecutors named Wells as an unindicted co-conspirator, saying he had a limited role in the plot -- something his family denies.