The final witness for gays and lesbians seeking to overturn California’s ban on same-sex marriage testified Friday that most people don’t choose their sexual orientation, few people change it and “conversion therapy” is useless and potentially harmful.

“The vast majority of people are consistent in their (sexual) behavior, their identity and their attractions,” Gregory Herek, a UC Davis psychology professor, said at the San Francisco federal court trial on the constitutionality of Proposition 8.

He said 95 percent of the self-identified gay men in a study he conducted, and 80 to 90 percent of the lesbians, believed they had little or no choice in their sexual orientation. Gays and lesbians commonly have heterosexual partners at some point in life – typically due to youthful uncertainty and social pressures – but most people ultimately can define their own sexuality, Herek said.

Read the rest of Bob Egelko’s San Francisco Chronicle article here.