NEW YORK, March 21 (Reuters) - A U.S. judge said on Wednesday that advocating for jury nullification could pose a threat to the judicial system, particularly if it takes place close to potential jurors.

U.S. District Judge Kimba Wood made the comments in the case of Julian Heicklen, of Teaneck, New Jersey, a retired, 80-year old chemistry professor who was charged and arrested after distributing pamphlets advocating jury nullification outside federal court in Manhattan.

The pamphlets called on potential jurors to follow their conscience in returning a verdict, and urged them to find a defendant not-guilty if they disagreed with the law in question or the government's conduct in the case.

"Juries were instituted to protect citizens from the tyranny of government," said one pamphlet, submitted by the defense as part of a brief. "It is not the duty of the jury to uphold the law. It is the jury's duty to see that justice is done."

In defending Heicklen, attorney Steven Statsinger told the court that jury nullification "really is not a serious threat to the integrity of the system."

"I disagree with that," responded Judge Wood, who brought up the possibility of jurors voting to acquit a person based on ideological beliefs, such as "pro-life protesters who believe that it should be lawful to kill an abortion provider, an eye for an eye, a life for a life."

Heicklen, who is representing himself with the aide of Statsinger, is charged with one count of jury tampering, which carries up to six months in prison.

Prosecutors say that jury nullification is unlawful, and that by encouraging it, Heicklen was undermining the good functioning of the court system.

Prosecutors also argue that Heicklen could not claim free speech protection because he was handing out pamphlets on federal property -- the plaza at the 500 Pearl Street entrance of the Manhattan Federal Courthouse -- and was specifically targeting potential jurors.

"The thing here that is so troubling to the government is that the message... undermines the fundamental fairness of our system," Assistant U.S. Attorney Rebecca Mermelstein said at Wednesday's hearing. "If a person is on the steps of a courthouse and is trying to influence jurors, that is a crime."

Mermelstein conceded that if Heicklen was "further from the courthouse, the less likely he is to be violating the statute."

Statsinger responded that the plaza in question was a public forum where "expressive activity" routinely takes place and that Heicklen's activity was "pure advocacy" not aimed at any particular juror or trial.

The case is U.S. v. Julian Heicklen, U.S. District Court for the Southern District of New York, No. 10-1154.

For the government: Assistant U.S. Attorney Rebecca Mermelstein.

For Heicklen: Heicklen is representing himself and is assisted by Sabrina Shroff and Steven Statsinger of the Federal Defenders of New York.

(Reporting By Basil Katz)

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