The Michigan Supreme Court, reversing an appeals court ruling, said yesterday that two University of Michigan students can not be forced to reveal their votes in a disputed mayoral election, even though those votes were illegally cast.

The court ruled unanimously that a citizen's constitutional right to a secret ballot cannot be abrogated unless intended fraud can be proven.

The case stems from a suit filed by Louis Belcher, a Republican City Councilman who lost the mayoral race last April to incumbent Democrat Albert Wheeler by one vote.

It was discovered last summer that faulty street guides had been used, allowing 20 voters who actually lived outside the city to register and vote. Belcher filed suit against Wheeler, claiming that Wheeler was holding that mayor's post illegally.

Last October, Judge James Kelley ruled that the 20 voters could be asked to tell how they voted. When Susan Van Hattum, a 21-year-old pre-law student, refused to tell on the grounds that it was her constitutional right to keep her vote a secret, she was cited for contempt. Later another student, 28-year-old Diane Lazinsky, also refused to tell and was also cited for contempt.

In November, the Michigan Court of Appeals upheld Kelley's ruling, saying that the right of secrecy in voting does not extend to anyone voting illegally, whether fraud was intended or not. Lawyers for Van Hattum and Lazinsky appealed to the Supreme Court, leading to yesterday's decision.

Van Hattum said that the knowledge of law she had attained through her work with a local tenants' union helped her to dare to say no to the judge.

"It's just real important that the vote be secret," she said. "I'm happy I did it and if I had to I'd do it again."

Lazinsky could not be reached for comment.