The state NAACP, labor unions and other groups criticized the controversial Republican-backed legislation, which requires voters to provide certain types of photo ID before they can cast a ballot.
"It's a ploy to take votes away from the people who deserve them," said John Jordan of the Pennsylvania Voter ID Coalition. He urged people to "vote your values, and value your vote."
The trial, starting Monday in Commonwealth Court, will examine the law's constitutionality against a challenge led by the state American Civil Liberties Union. They want the court to prevent enforcement of the law while the court challenge is pending.
Supporters of the law say it is a sensible way to prevent voter fraud, while those against it say it is designed to tamp down turnout by minorities and other Democratic-leaning groups.
The court prevented the law from taking effect last year. Defending the law are lawyers for GOP Gov. Tom Corbett and Democratic Attorney General Kathleen Kane.