A retired U.S. government scientist, Shepter spent his final two years dwelling in a nursing home in Mountain Mesa, Calif., a small town northeast of Bakersfield. A stroke had paralyzed much of his body, while dementia had eroded his ability to communicate.

He died in January 2007 at age 76. On Shepter’s death certificate, Dr. Hoshang Pormir, the nursing home’s chief medical officer, explained that the cause was heart failure brought on by clogged arteries.

Shepter’s family had no reason to doubt it. The local coroner never looked into the death. Shepter’s body was interred in a local cemetery.

But…