UNTIL WE READ the news story from Ann Arbor the other day, it had not occurred to us that you could be sent to jail for refusing to tell how you voted in an election. But a judge did just that recently to Susan R. VanHattum, a 21-year-old student at the University of Michigan. He ordered her to tell him who she had voted for in a city election. She refused, and he sent her to jail for contempt of court. She was released after an hour and a half, but she will be back in court soon to defend herself further against the contempt charge.

The judge's rationale was that he needed to know how 20 people cast their ballots in a city election last spring. They voted illegally - through no fault of their own but because of a mistake in the voter-registration office - and the result of the election is being contested. If the judge can find out how these 20 persons voted, he can deduct their votes from the final tallies and resolve a serious election contest without either requiring a new election or putting into office a mayor who may have been chosen by invalid votes.

Now that may well be as good an argument as any that could be made for violating the secrecy of the ballot box. But as far as we are concerned, it is not nearly good enough.If voters are to cast their ballots in secret, how they cast them must remain secret unless they choose to tell. The government - in the form of a President, a state legislature or a judge - has no business even asking how a particular person voted. The idea that government should put people in jail for refusing to answer that question is alien to the principles on which this nation operates. If a judge can compel a young women to reveal how she voted for the particular reason advanced in this case, another judge can find another reason for compelling someone else to make a similar revelation. Miss VanHattum ought to get a medal for her willingness to go to jail rather than submit to such an abuse of power.