Washington -LRB- CNN -RRB- -- An American lawyer has been holding secret negotiations with Iran for the release of an Iranian-American being detained for two years . Reza Taghavi , a retired businessman from Orange County , California , has been held in Iran 's notorious Evin prison since his arrest in May 2008 without ever being charged , his lawyer said . Los Angeles-based attorney Pierre Prosper told CNN he has been talking to the Iranian government since September 2009 and traveled to Tehran in December to seek the release of Taghavi , a retired businessman accused of supporting an anti-regime group . Taghavi , 71 , traveled frequently to Iran to visit family and friends without incident , according to Prosper . In April 2008 , he went to Tehran with his wife . Before he left , he was asked by an acquaintance in Los Angeles to take $ 200 for a friend in Tehran `` who was down on his luck . '' Los Angeles has a large Persian community . Taghavi did not know the individual to whom he was asked to deliver the money , Prosper said . He handed over the money and two weeks later was detained by Iranian authorities , after the recipient of the money was arrested on charges of association with an anti-regime group called Tondar . The group , which seeks to restore the monarchy in Iran , claimed responsibility for the April 12 , 2008 , bombing of the Hosseynieh Seyed al-Shohada mosque in the city of Shiraz . Prosper declined to name the man , who he said has since been tried and convicted . Taghavi has a rag-to-riches story , his 36-year old daughter , Leila Taghavi , told CNN . He brought his family to the United States in 1979 , before the revolution , and stayed on in California to keep his family safe . Leila Taghavi said her father taught himself English , started a video game company in his garage and grew it into a successful corporation , which he handed over to his son when he retired 10 years ago . `` His life was the American dream , '' Leila said . `` He learned everything the hard way , sacrificed for his children and taught us to be grateful for the good things . He is wonderful , honest and generous , the kind of father every daughter would want . '' Taghavi 's family was silent for more than a year about his arrest , fearful his arrest would be politicized in Tehran and Washington by getting the American government involved . `` It was blind faith , really , '' Leila said , explaining the silence . `` Not knowing it would take this long , and fear of the system . There was never a doubt of his innocence . '' In September 2009 , with no movement on the case and losing hope he would be released , they hired Prosper to contact the State Department and initiate a dialogue with the Iranian government . Prosper said he contacted the State Department about seeking a consular visit by Swiss diplomats , which was denied because Iran does not recognize the dual citizenship of Iranian-Americans . The United States and Iran do not have formal relations , and Switzerland serves as the `` protecting power '' for the U.S. in Tehran . A U.S. State Department spokesman urged Iran to allow Swiss diplomats to be granted consular access to Taghavi . `` We are adamant that we believe he should be released on humanitarian grounds along with all the Americans who are unjustly held there , '' Mark Toner , a State Department spokesman , told CNN Wednesday . A senior government official who met with Prosper said the lack of information makes it difficult to help Taghavi . `` As far as we are concerned , there are no facts in the case , '' the official said . `` Our concern is that he should get due process . '' Taghavi is one of several Americans in prison in Iran . American hikers Josh Fattal , Shane Bauer and Sarah Shourd were detained on July 31 , 2009 . According to their families , they accidentally strayed across an unmarked border into Iran while on a hiking trip in Iraq 's Kurdistan region . They are being held on espionage charges . Kian Tajbakhsh , an Iranian-American scholar who spent four months in jail in 2007 , was arrested in July after the disputed presidential election and sentenced to 15 years in jail for spying . His sentence was later reduced by an appeals court to five years , and a State Department official tells CNN he has been released for two weeks from jail to celebrate the Persian New Year . The United States has no information about Robert Levinson , a former FBI agent who disappeared in Iran almost three years ago . After being hired by Taghavi family last September , Prosper said he contacted the Iranian Permanent Mission to the United Nations and was granted a meeting with the ambassador , who eventually put him in touch with Iran 's foreign ministry . After several months of weekly contact with Iranian officials in New York and Tehran , Prosper was invited to Iran in December for talks about Taghavi 's case . Prosper said he was briefed on the Iranian view of the case but was told the authorities were still investigating the matter . `` It 's still not clear what the accusations actually are , '' he said . Prosper left Tehran without being allowed to see Taghavi , but he was taken to visit victims of the 2008 mosque bombing by Tondar in an Iranian effort to show him the threat the regime says it 's facing from `` terrorist groups '' being financed from sources abroad . `` I think they had me meet with victims and survivors of the bombing to let it be known that they , too , in their eyes had experienced terrorism , '' Prosper said . It is unclear why the Iranian government invited Prosper , who served as the ambassador-at-large for war crimes under the Bush administration and as a prosecutor for the Rwanda tribunal at the Hague , for talks in Iran . Beyond talking about the case and attacks at the hand of the Tondar group , Prosper said his Iranian hosts made no effort to broaden the discussions to include the nuclear standoff between Iran and the West or the Obama administration 's offer of engagement . The facts of the case remain a mystery . Taghavi 's family maintains he is innocent and has never been involved in political activism against the Iranian regime . Prosper acknowledged the case has been a challenge to investigate because of his inability to question people in Iran and the lack of information from the government or Taghavi 's Iranian lawyers in Tehran , who do n't speak English . But based on his discussions with the family and his own `` due diligence , '' Prosper said he believes Taghavi is an innocent man , whose only crime is guilt by association . As a former prosecutor , Prosper said he believes if the Iranians had a case against Taghavi , they would have already tried him . He 's seeking a humanitarian release for Taghavi , who suffers from diabetes and whose health is deteriorating in prison , according to his family . The political upheaval in Iran after the disputed presidential election and subsequent violent crackdown on demonstrators has complicated his efforts , the lawyer said . `` It casts a shadow over our efforts , '' Prosper acknowledged . `` What I 've been doing to my best ability is to cut through that , cut through the fog that has been created , focus on Mr. Taghavi and work with the Iranian authorities on the substance of what happened in 2008 . '' Leila Taghavi traveled to Iran last year and was allowed a brief visit with her father in prison . `` I saw him behind a window , '' she said , choking back tears . `` It was painful to see your father , an innocent man , behind a window . '' `` We are chipping away at this , '' Prosper said . `` I want to give them credit for the dialogue , but the proof will be in the results . We are holding out hope because that is the only thing we can do . ... Effectively his life is at stake . '' Leila spoke with her father by phone Wednesday morning and said he sounded tired and anxious . `` My biggest hope is that this message reaches people and somebody can do something , '' Leila added . `` Not just for my father , but for the many people that are trying to get their loved ones out of Iran . ''