Professor Michael Lamb, fellow of Sidney Sussex and head of the Social and Developmental Psychology Department, has testified as an expert witness for the infamous Proposition 8 trial currently taking place in San Francisco.

Proposition 8, also known as the California Marriage Protection Act, was passed last year by a state-wide vote, overturning the right of same sex couples to marry by defining marriage as a union between one man and one woman. The trial’s plaintiffs, two same sex couples, are suing the state to repeal the measure.

The plaintiffs claim that Proposition 8 is unconstitutional in violating the 14th Amendment, which guarantees equal protection of the law to all American citizens.

Professor Lamb, who researches parent-child relationships and the development of psychological adjustment, testified that there is “substantial evidence” that children of same-sex couples grow up as well-adjusted as children of heterosexual couples.

“It is beyond scientific dispute that the factors that account for children's adjustment,” Professor Lamb later wrote, “are the quality of children's relationships with their parents, the quality of the relationship between the parents or significant adults in the children's lives, and the availability of economic resources. These factors are the same in both traditional and non-traditional families.”

He added, “The parents' sex or sexual orientation does not affect the capacity to be a good parent or children's healthy development. There is also no empirical support for the notion that children need both male and female role models in the home to adjust well.”

Professor Lamb’s testimony was met with strong opposition from the defense lawyers. During questioning, defense attorney David Thompson tried to suggest that Professor Lamb’s field is too suffused with politics for his testimony to be considered sound evidence, by having Professor Lamb acknowledge that he is “a liberal”.

The trial is distinctive for having relied on the testimonies of numerous renowned academics. In addition to Professor Lamb, four other expert witnesses have testified for the plaintiff: Nancy Cott, a Harvard University historian of women’s issues and marriage; George Chauncey, a Yale University expert on the history of LGBT discrimination; Letitia Peplau, a UCLA professor who studies couple relationships; and Ilan Meyer, a Columbia University member who testified on social stigmas.

The trial would also have set a precedent in being the first federal trial to be streamed live in several courthouses and on YouTube. However, the Supreme Court ruled five to four to block live streaming after the defendants filed emergency papers to bar the telecast.