“I was very surprised, when I opened my e-mail account on June 21 and found over 60 people from all over the world who had added me on Facebook” as a friend, Ms. Soltani said. That number kept growing, puzzling Ms. Soltani and her mother, until they saw her picture on television, cast as a victim of Iranian security forces.

She said she and her friends started to contact media outlets to tell them that she was not the woman in the YouTube video. Even when the family of the slain woman released photos of her on June 23, Ms. Soltani’s pictures were still used in news reports and on Web sites.

By June 24, the Iranian intelligence service started looking for her, Ms. Soltani said. Panicked, she contacted Amnesty International in London. “She was very afraid and scared and did not know what to do,” said Ann Harrison, a researcher on Iran for Amnesty International. “She came across as a person who was not involved in politics, who used to have a quiet life.”

The group, which considers Ms. Soltani’s account credible, later published a report about the repression of dissent in Iran; in a section on the case of Neda Agha-Soltan, it mentioned the fact that the photo had been used in error. A report on the mix-up also appeared on a BBC blog.

Agents from the intelligence service picked her up from her home outside Tehran and took her for questioning, Ms. Soltani said.

“They asked me to say on camera that I was still alive and that the Greek Embassy in Tehran had leaked my picture to the media and that the story was wrong,” Ms. Soltani said. (Her Facebook picture was identical to the one that she had given to the embassy weeks before in seeking a visa to the academic conference.)

“They wanted to use me to denounce Neda’s death,” she said. “They wanted to draw attention to me to show the world, look this is a lie.” They also wanted her to blame conspirators from the West for the episode.