The US trial on Proposition 8 entered its tenth day yesterday, with lawyers for gay marriage opponents opening their case.

Last week, lawyers for the plaintiffs, two gay couples from northern and southern California, argued that gays lack political clout and need more constitutional protection.

This is the first federal trial to examine whether Prop 8, which banned gay marriage in 2008, is constitutional.

Yesterday, the team defending Proposition 8, which banned gay marriage in California, called Claremont McKenna College professor Kenneth P Miller as their first witness.

Miller argued that gay marriage supporters managed to raise $43 million during their 2008 campaign, $3.4 million more than opponents raised.

This, Miller testified, was “exceptionally rare” for a ballot on social issues.

David Boies, an attorney for the plaintiffs, asked him whether gays and lesbians suffered more discrimination than ethnic minorities, who are granted equal rights under America’s constitution.

Miller refused to agree with this, although he agreed that lesbians faced more bias than straight women.

Under cross-examination, he cited the military gay ban and the Defence of Marriage Act as laws which treat gays and lesbians differently from heterosexuals but said he did not know whether this amounted to illegal discrimination.

Blogging on Miller’s testimony for the Courage Campaign’s online Prop 8 Trial Tracker, attorney Brian Leubitz described him as a “really defeated expert witness”. But he added that the lawyers acting for gay marriage supporters were still faced with an “uneven playing field”.

He wrote: “They have to roll the boulder up the hill. While Prof Miller seems to be struggling to push it down the hill, they are still the ones pushing the easy way.”

The trial resumes today, with continued testimony from Prop 8 supporters.

For previous coverage of proceedings, see related links below.