"And that is what you told people to try to convince them to vote yes on Proposition 8, correct?" asked David Boies, a lawyer for the challengers.

He also was asked about a statement that the gay agenda included legalizing sex with children.

"It is very important that our children won't grow up to fantasize or think about, 'Should I marry Jane or John?' " testified Tam, a chemical engineer and evangelical Christian.

William Tam, one of five official proponents for the 2008 ballot initiative, also testified about his personal views toward same-sex marriage.

An official proponent of Proposition 8 testified today that he was involved in disseminating claims that same-sex marriage could cause children to become gay and spark legalization of sex with children, incest and polygamy.

Tam said he participated in weekly campaign conference calls for grass-roots organizers run by the official campaign and sought advice from the campaign. He said he also played a major role in the petition campaign to get the measure qualified for the ballot.

Tam testified that he was secretary of an anti-gay marriage website that carried statements saying homosexuals were 12 times more likely than heterosexuals to molest children.

Tam said he agreed with the statement "based on different literature I have read. " He was unable to recall where he read it.

He also testified that a flier for Proposition 8 predicted dire results if gays were given civil rights.

"If sexual orientation is characterized as a civil right, so would pedophilia, polygamy and incest," the flier read.

"That is what you were telling people to convince them to vote for Proposition 8, correct?" Boies asked.

"Yes," Tam replied.

Boies noted that another statement said the gay agenda includes legalizing sex with children.

"And that is what you told people to try to convince them to vote yes on Proposition 8, correct? " Boies asked.

"Yes," Tam replied.

A lawyer defending Proposition 8 tried to distance Tam from the campaign.

Under cross-examination, Tam testified that he did not submit his materials and statements to the official Proposition 8 campaign for approval, nor were some of the fliers mentioned approved by the campaign manager.

--Maura Dolan at the San Francisco federal courthouse