When he eagerly joined the mass street protests that followed Iran’s tainted June 12 presidential elections, Ibrahim Sharifi, 24, hoped only to add his voice to the hundreds of thousands of demonstrators demanding that the government nullify the results. He never imagined that he would eventually have a far greater impact, as the only person willing to speak publicly about the brutal treatment he was subjected to in prison, including rape and torture.

Mr. Sharifi, who recounted his ordeal to the opposition leader and former presidential candidate Mehdi Karroubi, and then released a video account last month on opposition Web sites, is now in Turkey. He said he fled Iran after a stranger stopped him on the street to tell him his family would be killed if he testified before a parliamentary committee that was investigating the torture and rape accusations.

“I felt that I was not safe anymore and I could put my family’s life in danger, too,” he said in a series of telephone interviews, in which he spoke in detail about the protests, his imprisonment and the psychological scars he said the abuse had left.

Since he was dumped by his captors on the side of a Tehran highway, he said, he has been terrified of being alone. First, he had trouble sleeping, fearing that the guard who raped him in prison would attack him again. Now he is convinced he is being followed by someone who means to kill him.