Bob Egelko, San Francisco Chronicle May 15th, 2007 -- The retrial of marijuana advocate Ed Rosenthal on federal cultivation charges opened today with his lawyer doing everything she could to make it clear to jurors that he had been growing cannabis for medical use, a subject the judge has put off-limits.

"Mr. Rosenthal is a scientist and the government will attempt to suppress his ideas,'' defense lawyer Shari Greenberger said in an opening statement in San Francisco federal court that drew repeated objections from the prosecutor. "For the past 40 years, my client, Ed Rosenthal, has been a proponent of marijuana advocacy and reform, and that is why we are here.''

U.S. District Judge Charles Breyer immediately told the jurors they were there to decide whether Rosenthal was guilty of growing marijuana, not why the government was prosecuting him.

Rosenthal, 62, of Oakland, an authority on marijuana cultivation and writer of numerous books and magazine articles on the subject, was arrested in 2002 and charged with growing thousands of plants for patients at a San Francisco dispensary. He was convicted in 2003 but sentenced by Breyer to only one day in jail, which he had already served. The judge said Rosenthal had believed he was acting legally because the city of Oakland had designated him as an agent in its medical marijuana distribution program.

A federal appeals court overturned the conviction last year because of misconduct by a juror who had called an attorney for advice during deliberations. Prosecutors tried unsuccessfully to add charges of tax evasion and money laundering for Rosenthal's second trial and have acknowledged that he could not be jailed if convicted again.

As at the first trial, Breyer has barred evidence that the marijuana was intended for medical use, or to the 1996 California initiative that allowed patients to use the drug with their doctor's recommendation. That didn't stop Greenberger from trying.

Referring -- over prosecution objections -- to Rosenthal's numerous appearances as an expert witness in marijuana trials, the defense lawyer said, "His testimony for the defense on medical cannabis did not endear him to the federal government.''

Greenberger also said a federal undercover agent had gone to the San Francisco dispensary and "purchased marijuana that was intended for patients.''

She reminded the jurors, who were questioned about their attitudes toward medical marijuana during jury selection Monday, that "this is a federal case brought by the federal government. There are certain areas where we cannot go.''

By contrast, Assistant U.S. Attorney George Bevan described the case as a straightforward prosecution for marijuana cultivation. He reminded the jurors in his opening statement that they had promised to apply the law according to Breyer's instructions.

Rosenthal, Bevan said, operated a large, sophisticated indoor growing operation at an Oakland warehouse from August 1996 until the time of his arrest in February 2002, and sold thousands of plants to "so-called marijuana clubs throughout the Bay Area.''

He said the witnesses would include people who helped Rosenthal grow marijuana or bought plants from him.

Greenberger, without denying that Rosenthal was involved in cultivation, said the prosecutor was relying on testimony from "convicted felons, liars, drug addicts and thieves'' who had been granted immunity or leniency in exchange for their testimony.

The trial is expected to last about two weeks.

E-mail Bob Egelko at begelko@sfchronicle.com.