Updated

Timothy Muldowny's lawyers decided on an unconventional approach to fight his drunken driving case: They sought computer programming information for the Intoxilyzer alcohol breath analysis machine to see whether his test was accurate.

Their strategy paid off.

The company that makes the Intoxilyzer refused to reveal the computer source code for its machine because it was a trade secret.

A county judge tossed out Muldowny's alcohol breath test — a crucial piece of evidence in a DUI case — and the ruling was upheld by an appeals court in 2004.

Since then, DUI suspects in Florida, New York, Nebraska and elsewhere have mounted similar challenges. Many have won or have had their DUI charges reduced to lesser offenses.

The strategy could affect thousands of the roughly 1.5 million DUI arrests made each year in the United States, defense lawyers say.

"Any piece of equipment that is used to test something in the criminal justice system, the defense attorney has the ability to know how the thing works and subject its fundamental capabilities to review," said Flem Whited III, a Daytona Beach attorney with expertise on DUI defense.

The Intoxilyzer, manufactured by CMI Inc. of Owensboro, Ky., is the most widely used alcohol breath testing machine in the United States and is involved in the vast majority of these legal challenges.

It is used exclusively by law enforcement agencies in 20 states, including Florida, and by at least some police agencies in 20 other states, according to the company.

Most states have "implied consent" laws for motorists requiring DUI suspects to blow into a breath analysis machine if asked to do so by a police officer.

"The breath test is an integral part of any prosecution," said Earl Varn, an assistant state attorney in Sarasota.

In Florida, state law currently considers a breath test valid if the machine is approved by the Florida Department of Law Enforcement and the person administering the test is qualified.

The law also says that a defendant is entitled to "full information concerning the test taken" if such a request is made.

The meaning of that phrase is the key to the DUI challenges in Florida and other states with similar laws.

DUI defense lawyers insist that "full information" means every minute detail about the Intoxilyzer, including the source code used by its computer processor to analyze breath samples, should be subjected to review by expert defense witnesses. Some judges have agreed.

"It seems to us that one should not have privileges and freedom jeopardized by the results of a mystical machine that is immune from discovery," Florida's 5th District Court of Appeal ruled in Muldowny's case, which resulted in his charges being reduced to reckless driving.

Judges in the Florida counties of Manatee, Sarasota, Seminole and Volusia counties are among those who have ruled in recent months that the defense was entitled to the Intoxilyzer's source code to see if the test results are reliable.

There also have been successful legal challenges involving the source code of other machines, including a 2005 case in Bellevue, Wash., in which a defense lawyer obtained the code of the BAC Datamaster testing machine, sold by National Patent Analytical Systems Inc.

But many judges in Florida have ruled the opposite way on the Intoxilyzer, including a panel in Palm Beach County that recently denied challenges by 1,500 DUI defendants who sought the source code under state public records laws.

The tactic has led lawmakers to introduce a measure in the Florida Legislature to clarify that such source codes don't have to be produced for DUI defendants.

Last November, a similar challenge in Omaha, Neb., was rejected on grounds that Nebraska did not have the source code. In Rochester, N.Y., a DUI suspect whose lawyer was seeking the source code was convicted of a lesser charge when the technician who maintained the machine was unavailable to testify.

Because CMI has refused to divulge its source code, Florida officials have argued in court that they cannot produce it for DUI defendants. Although most state judges have upheld that view, others have not.

"The state may not wash its hands of its duty to produce this information by claiming that it does not have it," Volusia County Court Judge Mary Jane Henderson ruled in December.

FDLE officials say that even if the state had access to the source code it would not necessary to test the validity of the breath results.

Laura Barfield, alcohol testing program manager at FDLE, said each of the 408 Intoxilyzer 5000s used in Florida — soon to be replaced by the 8000 model — are regularly run through painstaking tests at the state and local levels.

"You don't need the source code to know the machine is providing accurate results," Barfield said.

For its part, CMI said there is no evidence that its Intoxilyzer is inaccurate, noting that a review of 80,000 tests in a 2002 Arizona case produced no evidence of mistakes.

In a statement to The Associated Press, the company said also said the source code is not a crucial element in proving the Intoxilyzer's accuracy and is a proprietary trade secret that could create havoc if computer hackers obtained it.

"Exposure of the source code could not only be detrimental to CMI from a commercial standpoint, but it could also be detrimental to customers of CMI," the company said. "Disclosure of this information could compromise the integrity of test data that is stored in the instrument."

The conflicting decisions around Florida could land the issue before the state Supreme Court. Florida lawmakers may act before that, however.

A bill making several changes to DUI law includes a section clarifying that the "full information" about breath tests does not include the "manual, schematics or software" of the breath machine or any information "in the possession of the manufacturer."

The bill is moving through state House committees and could pass later this year.

Prosecutors such as Varn say if the defense challenges prevail it would mean each DUI breath test could be subjected to exhaustive analysis.

"We would have to hire an expert to come in and testify in every case to explain the function of the instrument and what the test results mean," Varn said.

But defense lawyers say DUI defendants have the constitutional right to confront their accuser, even if it is a machine.

"If everything is OK and there's nothing to hide, why do they want to change the law?" said Stuart Hyman of Orlando, a leading DUI defense lawyer who represented Muldowny. "It's ludicrous."