Defenders of California’s ban on same-sex marriage wrapped up their case in federal court here Wednesday after a tense cross-examination of their expert witness by a lawyer representing gay couples.

Defense witness David Blankenhorn, president of the Institute for American Values, had testified Tuesday that marriage by nature is a heterosexual institution designed to promote parenthood. He said allowing gay weddings would weaken the institution, likely leading to lower marriage rates and higher divorce rates for heterosexuals, as well as possible social acceptance of polygamy.

Under aggressive questioning from plaintiffs’ lawyer David Boies on Wednesday, Mr. Blankenhorn said same-sex weddings could benefit gay couples and their children. “I believe it would be likely to do that,” Mr. Blankenhorn said.

Read the rest of Stu Woo’s Wall Street Journal article here.