Just a month after Salt Lake County commissioners joined other local leaders in pledging not to raise property taxes except in an emergency or by a vote of the people, a proposed new jail may test that pledge.

Commissioners have discussed ballot language for an expected May 23 special jail-bond election. The bond proposition will determine whether the election is a referendum on jail construction or merely gives voters a chance to approve a tax increase that will occur even if the bond is voted down.Simply stated, how commissioners write the ballot question will decide what happens if voters reject the general-obligation bond issue - and the corresponding property tax increase - to fund jail construction.

"If voters approve the bond, as we hope happens, there won't be a problem," said Commissioner Bart Barker. "If they don't approve the bond, then we have to make some hard choices."

The phrasing of the ballot question will either give voters a true choice between raising property taxes and not raising them, or it will assume that taxes must rise and ask voters to decide by how much.

A voter-approved bond issue is the least expensive way for the county to borrow money to fund construction of the 350-bed minimum-security facility officials say is needed. The county can use other methods to borrow, but all are more expensive.

Architects estimate the jail will cost about $9.9 million, not including design and consulting costs that could push the figure higher. Commissioners are not ready to say how big a bond issue they will ask voters to approve, only that it will be in the $8 million to $12 million range.

County budget officials estimate that would cost the owner of a $75,000 home about $2.75 to $3 more in annual property taxes.

Here's how commissioners' ballot language choices shape up:

-If the ballot question simply asks whether bonds should be issued and taxes raised to build a jail, voters may infer that the election is a jail referendum - meaning a negative election outcome is a public decree not to build any jail.

-If the ballot question clearly states that the jail will be built regardless of election results, voters will understand a "yes" outcome means the jail will be built at the least expense to the county - and thus with the lowest possible tax increase - while a "no" vote means either an even higher tax hike or spending cuts in county programs.

Commissioners have not reached a consensus on ballot language. Commissioner Mike Stewart clearly favors the second option, but Barker and Commissioner M. Tom Shimizu have said they need more time to study the language.

None of the alternatives open to commissioners in the event of a "no" vote is very attractive. Raising taxes to build the proposed facility after voters reject the jail bond undoubtedly would be an unpopular decision - one voters are not likely to forget by 1990, when commission seats held by Barker and Shimizu are up for re-election.

Commissioners have already made deep cuts in this year's county budget. Another $12 million in cuts would be difficult to achieve.

And the existing downtown jail is badly overcrowded. Official capacity is 550 inmates, but the March average daily occupancy is more than 670 prisoners, with a one-day peak of 707, said County Attorney David Yocom.