(FORTUNE Magazine) – As federal prosecutors continue to cast their nets in Wall Street's scandal- ridden seas, some innocents may also get snared. Michael Singer, 38, a former vice president at Salomon Brothers, claims he is one. Singer talked freely to FORTUNE, but would not pose for a photograph in which he would be recognized. Last November, on the same Friday that the SEC announced its insider trading case against Ivan Boesky, court officers subpoenaed Singer to testify to the SEC about his former employer, Boyd Jefferies, the now-fallen chairman of Jefferies & Co. Four days after receiving the subpoena, Singer says, he was forced to resign. Even though the SEC and the U.S. Attorney's office have since made it clear that Singer faces no civil or criminal charges, Salomon has refused to reinstate him, and no other large firms will consider him for a job. Says Singer: ''I am massively tainted simply because I was asked a question.'' At Jefferies, Singer had been a director in charge of a corporate finance group operating out of a New York office that, coincidentally, was in the same midtown skyscraper as the headquarters of Ivan Boesky & Co. In 1985, Boyd Jefferies phoned Singer with an urgent request that Singer's secretary type and deliver a detailed invoice for $3 million to Boesky's offices that day. Singer followed orders. A Salomon official, in defending his firm's decision to part company with Singer, wrote to him saying, among other things, that delivering the invoice showed poor judgment. The invoice turned out to be a key piece of evidence that Boyd Jefferies was doing secret stock trades for Boesky in violation of SEC disclosure rules. Singer has recently enlisted the help of Alan Dershowitz, a well-known Harvard Law School professor and criminal lawyer. One of Dershowitz's first actions was to write to U.S. Attorney Rudolph Giuliani. Giuliani's reply: ''It would be a deep injustice if Mr. Singer lost employment solely because he was subpoenaed by the U.S. Government.'' Dershowitz adds that firing people for complying with a subpoena constitutes an interference with their civil rights and with Justice Department investigations. He warns: ''The Singer case could be the tip of the iceberg.''