For some, it comes once a lifetime. For others, it never comes.
For Vaughn Walker, it came on an ordinary day in May 2009, as the San Francisco-based retired federal judge was digging through a pile of paperwork.
That was when the "quietly but openly" gay judge found out that he would be called to rule on Perry vs. Schwarzenegger, the challenge to Proposition 8, California's ban on same-sex marriage, according to the San Jose Mercury News.
"That's when I had the 'Oh (my) moment,'" Walker told the newspaper.
Walker was close to retirement when the suit was filed, but he stayed on the bench -- and set into motion a chain of events that will culminate next month, when the challenge to the voter-approved ban on same-sex marriage is heard at the United States Supreme Court.
Walker in 2010 ruled that the ban was unconstitutional, without social justification and singling out same-sex couples for discrimination -- unequal treatment under the law, the newspaper reported. A federal appeals court largely agreed.
Prop. 8's backers have put forth a weak case for defending their law, Walker says -- only two witnesses appeared in court to try to defend the law, he noted, and later, it seemed Prop. 8 backers' best effort to overturn his ruling was to point out that he is gay and therefore biased.
"It was their Hail Mary," he said.