Facing painful accusations of drunk driving, Dale Lee Underdahl of Minnesota challenged the accuracy of the Intoxilyzer 5000EN breathalyzer used against him, and demanded to see the source code used in the device.

The claim launched debates and a lawsuit that escalated all the way to the Minnesota Supreme Court. The device’s manufacturer, CMI, Inc. of Kentucky,claimed the source code was proprietary, copyrighted and refused to comply.  To that end, CMI attempted to block the source code’s release by filing a writ of prohibition, which was denied by the Minnesota Supreme Court, who said the writ is “an extraordinary remedy and is only used in extraordinary cases.”

The State of Minnesota specifically commissioned the Intoxilyzer 5000EN model and “all right, title, and interest in all copyrightable material” created “will be the property of the state,” according to the state’s original bid proposal. Furthermore, the proposal also said CMI must provide the necessary information to “attorneys representing individuals charged with crimes in which a test with the proposed instrument is part of the evidence,” which according to CNet, “seems to include source code.”

On July 26, the Minnesota Supreme Court ruled in Underdahl’s favor, assuring the discoverability of the devices source code and affirming his right to its examination. “The problem is, the manufacturer of the thing thinks they can hold it back and not tell anybody how it works. For all we know, it's a random number generator,” said Underdahl’s attorney, Jeffrey Sheridan.

The Minnesota Department of Public Safety has expressed reluctance to forcibly acquire the source code, and according to a department spokesman, is still considering its response. The department thinks a lawsuit is unnecessary as the contract stipulates CMI’s cooperation with court orders.

The “source code defense” has been used in a number of other states with mixed success. Manufacturers, in the interest of guarding their trade secrets, have rigorously fought against court-ordered scrutiny. In one instance, judges in Florida’s Seminole County threw out hundreds of cases involving breath tests because the manufacturer would not disclose their breathalyzer's source code. However, in another instance a group of more than 150 suspects, in Florida’s Sarasota County, were granted access to the machines’ source code, with the judges citing it was “material to their theory of defense in [their] cases.”