Minnesota Court Orders Release of DUI 'Breathalyzer' Source Code
• By David Kravets, May 11, 2009, 7:14 pm
Drunken-driving convicts in Minnesota are intoxicated over a recent state high court ruling allowing defense experts to examine the source code of breath-testing machines.
The legal brouhaha concerns the court's position (.pdf) that drunk drivers have the right to examine the evidence against them. But the company that supplies the state with breath-testing machines, CMI of Kentucky, isn't forking over the code and is declaring it a trade secret — threatening thousands of DUI convictions.
Princeton computer science whiz Ed Felten and others point out the conundrum.
"The problem is illustrated nicely by a contradiction in the arguments that CMI and the state are making. On the one hand, they argue that the machine's source code contains valuable trade secrets — I'll call them the 'secret sauce' — and that CMI's business would be substantially harmed if its competitors learned about the secret sauce," Felten writes on the Freedom to Tinker blog. "On the other hand, they argue that there is no need to examine the source code because it operates straightforwardly, just reading values from some sensors and doing simple calculations to derive a blood alcohol estimate."
The state and CMI are involved in a separate legal flap about whether the maker of the Intoxilyzer 5000EN should turn over the code to the state.
Still, internet security guru Eric Rescorla points out another problem: that an examination of the source code may not help determine whether the machines are reliable.
"Stepping up a level, it's not clear what our policy should be about how to treat evidence from software-based systems; all software contains bugs of one kind or another (and we haven't even gotten to security vulnerabilities yet). If that's going to mean that all software-based systems are useless for evidentiary purposes, the world is going to get odd pretty fast," he writes on Educated Guesswork.
What's more, an analysis of the source code of the Draeger Alcotest used in New Jersey found frightening software errors as well. But that state's high court last year ruled against challenges questioning the machines' veracity.
"Despite the clear errors in the machine," Evan Levow, a New Jersey drunken-driving defense attorney said in a telephone interview, "the Supreme Court in New Jersey found the Alcotest to be reliable."