SACRAMENTO -- A federal prosecutor who led the investigation into doping allegations involving Lance Armstrong and others in professional cycling is also one of the attorneys in charge of the current corruption probe involving state Sen. Ronald S. Calderon (D-Montebello).

Assistant U.S. Atty. Douglas M. Miller surfaced in the Calderon case Friday when he issued a letter at the request of Sen. Kevin de Leon (D-Los Angeles), who has been subpoenaed in the case, indicating that De Leon is not the target of the investigation.

“Please accept this letter as confirmation that, at this time, Kevin de Leon is viewed as a witness in this Office’s ongoing investigation,” said the letter from Miller and Assistant U.S. Atty. Mack Jenkins that was addressed to an attorney for De Leon..

The two prosecutors are part of the Public Corruption and Civil Rights Section of the U.S. Attorney's office in Los Angeles.

“The assessment that he is a witness, as opposed to a subject or a target, is based on the information we have obtained to date," the letter said. "Of course, this assessment could change in the event that new and different information regarding your client comes to our attention.”

De Leon requested the letter after his name appeared in a sealed FBI affidavit as someone Calderon tried to influence on legislation on worker’s compensation laws to benefit a man who had allegedly paid bribes to Calderon. The affidavit was released this week by Al Jazeera America, triggering a federal investigation into the leak of a sealed document.

Miller has had to deal with leaks before.

The U.S. Attorney’s Office last year decided against filing criminal charges against Armstrong after the cyclist’s attorneys alleged in court papers that government sources had leaked confidential grand jury information "with the transparent agenda of publicly smearing Armstrong and aggrandizing the government's investigation."

Miller also led the U.S. attorney’s 2004 probe into who leaked confidential grand jury testimony concerning former San Francisco Giants slugger Barry Bonds and other baseball players in the BALCO doping case. That investigation resulted in a private attorney being sentenced to prison for leaking the documents.

Reached by telephone Friday, Miller declined to discuss the Calderon case or his role in it.

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patrick.mcgreevy@latimes.com