U.S. lawyers have presented closing arguments in a trial that could land a guru of the pro-marijuana movement in prison for the rest of his life, even though California deems his actions legal.

Ed Rosenthal, 58, has never hidden his enthusiasm for the weed and has written numerous books on the subject, including "Marijuana Grower's Handbook: The Indoor High Yield Guide" and "Marijuana Question? Ask Ed".

He now faces three counts of violating U.S. federal law for growing marijuana plants last year and, if convicted and given the maximum sentence, could face life in prison. He is charged with growing more than 3,000 marijuana plants for distribution to medical marijuana clubs.

In closing arguments, defense attorney Robert Eye ridiculed two government Drug Enforcement Agency witnesses who testified in the case - -- including one who called marijuana a "biohazard" -- and asked jurors to disregard their testimony.

Eye also appealed to the jury to base their verdict on life experience, prompting the judge to remind jurors of their obligation to follow the law rather than personal sentiments.

"Is this really a case of getting dangerous drugs off the street? Of course not," Eye told the jury.

Prosecutor George Bevan, an assistant U.S. Attorney, told the jury the defense had ignored the evidence in the case and was improperly asking the jury to send a message in their verdict.

"The counsel is saying base your decision on something other than the evidence," he said in closing, adding, "Your decision in this case must be based on the evidence."

In a short interview outside court, Rosenthal said the city of Oakland had authorised him to grow the plants, and he produced an identification card from his wallet reading: "Oakland Cannabis Buyers Cooperative."

"I was told by the city of Oakland that what I was doing was totally legal," said Rosenthal, a balding man with short hair, glasses and a suit.

"What the government wants to do is put a saw via the court through the whole medical marijuana movement," he said after final arguments in the case. "I think to the government I was a trophy."

Pot in the Jury Room

The court case also marks the latest battle over medical marijuana between the nation's most populous state and the federal government, which has recently been cracking down on California clubs providing the drug to ill patients.

Nine states, including California, permit medical use of marijuana under state law. The drug often relieves pain and nausea and increases appetite, but is outlawed in most of the United States because of the hallucinogenic high it produces.

The state measures contradict federal law. The U.S. Supreme Court in 2001 ruled that clubs providing marijuana to sick patients were breaking federal law.

"What we have in this country is a tremendous policy conflict between federal, state and local law," said William Dolphin, who is following the case for the Medical Marijuana Legal Defense and Education Fund, a group backing Rosenthal.

Rosenthal's lawyer, Eye, also requested that the evidence be placed in the room as jurors decide their verdict. "You want all of the marijuana in the jury room?" Judge Charles Breyer asked Eye.

"Yes," the attorney said, referring to the six sealed cartons labelled Drug Enforcement Agency evidence. The request was allowed.

The jury will begin their deliberations on Friday.

"That means I won't have a father at my high school graduation or even my college graduation," adolescent daughter Justine Rosenthal told Reuters when asked about the possibility of a guilty verdict. "My life would be ruined."