Children raised by gay and lesbian couples develop just as well as those brought up by traditional couples, a British child psychologist told a U.S. federal court considering whether a California ban on gay marriage denies constitutional rights.

Children raised by gay and lesbian couples develop just as well as those brought up by traditional couples, a British child psychologist a U.S. federal court considering whether a California ban on gay marriage denies constitutional rights.

Pedophile priests and whether the number or gender of parents was most important were core topics in testimony.

Lawyer David Thompson, defending the ban, jousted with Michael Lamb, head of the Social and Developmental Psychology Department at Cambridge University, about whether a child growing up without a father or without a mother would face developmental problems.

Two gay men and two lesbian women are asking the federal court to rule the right to marry has no exceptions under the U.S. Constitution, a fight they hope to take all the way to the U.S. Supreme Court in a bid to overturn bans on same-sex marriage in 40 states.

A key question in the case is whether government, and U.S. voters, have a reasonable justification for denying same-sex couples the right to marry, such as promoting healthier families, or if the bans reflect discrimination and hatred.

The record of evidence gathered by Federal District Chief Judge Vaughn Walker, including the issue of whether gays are good parents, may be relied upon heavily by appeals courts, which generally do not have as much time to review a case as in the original trial.

Walker asked one of the most striking questions of the day -- what the rash of pedophile priests suggested about the abilities of gays and lesbians in bringing up children.

"You've testified that there is no reason to protect children from lesbians and gays," said Walker. "How do you square your statement with that phenomenon," the judge asked.

"I don't want to convey the fact that homosexual individuals never abuse children, simply that they are no more likely to do so than heterosexual individuals," Lamb replied.

A witness for the same-sex couples, Lamb argued that the quality of the relationship between a child and parents, the relationship between the parents, and the economic resources available to the family were the top issues for healthy children -- not the gender or sexual preference of parents.

Kids had no trouble with their own sexual identity or other development due to growing up with same-sex parents, he argued, and the ways fathers and mothers interacted with kids was not as important as having two parents, he said.

"Children clearly benefit when they have two parents, both of them actively involved," said Lamb. Asked if mothers and fathers interacted differently with children, he replied, "It is now quite clear that those differences in and of themselves do not significantly affect children's adjustment," he said.

Thompson questioned the validity of dozens of studies.

"Dr. Lamb likes to talk about this rich deep literature and he doesn't have any studies that are married, biological parents," the optimum for raising children, Thompson told the judge. Instead studies mixed married and unmarried heterosexual couples, which Lamb conceded was often the case.

But Lamb said the conclusions were sound and pointed to a new study based on total U.S. census data that showed children raised by gay and lesbian couples were no more likely to be held back in school.

Proponents of the gay marriage ban will produce their own witnesses later in the trial and attempt to show there is good reason to believe homosexual parents endanger children.

Passage of the ban known as Proposition 8, in November 2008, stunned gay advocates in the United States and ended same-sex marriage in California, whose Supreme Court had legalized such unions early that summer.

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