Mr. William Robert Thompson was stopped by Minnetonka Police and requested to blow into the state's breath test machine. The machine determined Mr. Thompson had an alcohol concentration of .10.
Mr. Thompson challenged his license revocation asking the court to suppress the breath test result and to order the Commissioner of Public Safety to provide him with the machine's source code. Included in his request was an affidavit from Harley R. Myler, Ph.D., P.E. stating that without examining the source code, it would be impossible to determine whether the machine was operating properly at the time of Mr. Thompson's test. He also included two affidavits describing previous problems with the breath test machines used by Minnesota.
The Commissioner of Public Safety argued against the discovery request on the grounds that the state of Minnesota was involved in litigation against CMI (manufacturer of the Intoxilyzer) for breach of contract, breach of the implied covenant of good faith and fair dealing and copyright infringement.
The district court denied Mr. Thompson's requestt on the grounds that Mr. Thompson had failed to demonstrate that the source code was relevant to his defense. The court of appeals overturned the lower court's decision on the grounds that "the source code may reveal deficiencies in the accuracy of the Intoxilyzer 5000EN that would be relevant to a claim or defense..."
The tide is turning quickly on the "trade secret" defense used by CMI and the "it's not in our possession" defense used by prosecutors in DWI cases. The blueprint seems quite clear for obtaining breath test machine source code -- testimony from an expert regarding the need to examine the source to determine if the software functions correctly; evidence of machine malfunctions; case law from Kentucky, Minnesota and New Jersey where courts have ordered the state to turn over the source code; and, most importantly, a showing that an examination of the source code is relevant to the defense of the case.