WASHINGTON — A Pennsylvania woman convicted in a bizarre bank robbery that involved a pizza deliveryman with a bomb attached to his neck lost her Supreme Court appeal on Monday.

The justices, without comment, turned aside claims from Marjorie Diehl-Armstrong that she was innocent and mentally incompetent to stand trial.

Diehl-Armstrong, 63, was convicted of conspiracy and other charges related to the death of pizza deliveryman Brian Wells in 2003.

Authorities said Wells walked into a PNC Bank branch in Erie, Pennsylvania, on August 28, 2003, with a pipe bomb locked around his neck, and gave the teller a note demanding money. The robbery netted about $8,700.

Wells was killed when the bomb detonated as he sat in a parking lot after being stopped by police.

The case drew national attention and was the subject of an intense investigation.

Questions arose initially about whether Wells was a willing participant or a murder victim.

Prosecutors have long contended that Wells was involved in planning the robbery, but balked when he realized the bomb was real. They said he was threatened with a gun to make him wear it.

Diehl-Armstrong received a 30-year prison sentence in 2011.

“I am not a crazed killer,” she said at her sentencing. “The true killers are still out there.”

A federal appeals court rejected her appeal in November.

Diehl-Armstrong’s case was delayed because she underwent treatment after the judge in the case found initially that she was mentally incompetent to stand trial.

A third suspect was sentenced to 45 years in prison and a fourth died shortly after the robbery of a drug overdose, officials said.