At the height of Iran's bloody civil unrest this year, a young doctor named Ramin Pourandarjani defied his superiors. He refused to sign death certificates at a Tehran prison that he said were falsified to cover up murder.

He testified to a parliamentary committee that jailers were torturing and raping protesters, his family says. He told friends and family he feared for his life.

And on Nov. 10, the 26-year-old doctor was found dead in the military clinic where he lived and worked.

The family of Dr. Pourandarjani, who occasionally treated prisoners in fulfillment of Iran's obligatory military service, says he was killed for his refusal to participate in a coverup at the notorious Kahrizak detention center, widely criticized for its unsanitary conditions.

In a series of interviews over three weeks, Dr. Pourandarjani's family spoke in detail for the first time about their son's mysterious death.