PITTSBURGH — An Erie woman charged with helping plot an elaborate bank robbery that ended with the death of a pizza deliveryman who was wearing a bomb around his neck is not mentally competent to stand trial, a federal judge ruled Tuesday.

U.S. District Judge Sean McLaughlin agreed with a defense expert that Marjorie Diehl-Armstrong has bipolar disorder. The judge also noted her inability to work with her court-appointed lawyer.

He ordered her placed under the federal government's custody for hospitalization and treatment. He asked to be notified in 120 days — if she has not regained her capacity to stand trial sooner — whether there is a "substantial probability that in the foreseeable future from that date" that she will attain the capacity to permit the trial to go on.

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.