MINNEAPOLIS (AP) - Prosecutors in drunken-driving cases must turn over a breathalyzer's computer software as evidence in cases where a judge orders it and the defense has properly shown the information is relevant to a client's guilt or innocence, the state Supreme Court ruled Thursday.

If prosecutors can't produce the software - which the state currently does not have - the results of a breath test can't be used in court.

"It's a significant setback to law enforcement's ability to effectively and efficiently enforce our drunk driving laws in the state of Minnesota, at least for the current time being," said Dakota County Attorney James Backstrom.

In Minnesota, the results of alcohol breath tests are used in criminal drunken driving cases and in civil cases to revoke driver's licenses.

In some cases, defense attorneys have argued they have a right to analyze the software, or "source code," behind the Intoxilyzer breath-test machine so they can ensure the device was working properly. Judges in cities and counties throughout Minnesota have been split on the issue - with some ordering that prosecutors must produce the source code as evidence, and others ruling it isn't relevant.

Prosecutors have not been able to turn over the software because they don't have it; CMI of Kentucky, the company that makes the Intoxilyzer, has argued the software is a trade secret. The Supreme Court said Thursday that the state has possession or control of the source code, but the issue of access is currently pending in federal court.

An attorney for CMI did not return a phone call seeking comment. Law enforcement officials have said the machine works, and that requests for the source code are just attempts by the defense to get drunken-driving cases tossed.

Thursday's 18-page Supreme Court ruling still gives judges discretion on whether or not the software can be ordered as evidence.

However, the ruling essentially gives defense attorneys who want the software a blueprint for requesting it: The Supreme Court said that in one case where the defense provided detailed information about the software's relevance to his guilt or innocence, the district judge used proper discretion in ordering the software be turned over.

In a case where a defendant did not provide detailed information, the high court said, the district judge abused discretion when ordering the software allowed as evidence. Two justices, Alan Page and Paul Anderson, disagreed with that part of the majority opinion, saying the source code relates to guilt or innocence and a judge would be within discretion to order it as evidence.

"I expect this, at least in the short term here, to open the floodgates for source code demands now that we have a blueprint," said Marsh Halberg, a defense attorney who has been following the issue. "If I was a prosecutor ... I'd be saying, 'Let's just not do breath tests until this gets settled."

Backstrom said blood and urine tests are more costly and take longer to process. When authorities want to suspend the license of a suspected drunken driver, the quick results of a breath test allow them to do so within a week, while the wait for blood or urine results may mean months before a suspension.

The Minnesota Department of Public Safety was disappointed in the decision and is examining its options, which could include filing a motion for another hearing, said Andy Skoognan, a public safety spokesman.

"We also feel it is premature at this stage of the game for our law enforcement partners to only test for blood or urine," he said. "We still stand by the Intoxilyzer and the accuracy of the test results."

(Copyright 2009 by The Associated Press. All Rights Reserved.)