Researchers Say a Breathalyzer Has Flaws, Casting Doubt On Countless Convictions (zdnet.com)

An anonymous reader writes: The source code behind a police breathalyzer widely used in multiple states -- and millions of drunk driving arrests -- is under fire. It's the latest case of technology and the real world colliding -- one that revolves around source code, calibration of equipment, two researchers and legal maneuvering, state law enforcement agencies, and Draeger, the breathalyzer's manufacturer. This most recent skirmish began a decade ago when Washington state police sought to replace its aging fleet of breathalyzers. When the Washington police opened solicitations, the only bidder, Draeger, a German medical technology maker, won the contract to sell its flagship device, the Alcotest 9510, across the state. But defense attorneys have long believed the breathalyzer is faulty. Jason Lantz, a Washington-based defense lawyer, enlisted a software engineer and a security researcher to examine its source code. The two experts wrote in a preliminary report that they found flaws capable of producing incorrect breath test results. The defense hailed the results as a breakthrough, believing the findings could cast doubt on countless drunk-driving prosecutions.

Comments

Not in Europe

[Ubi_NL]

In .nl at least, these breathalyzers are used by police to do a quick test only. If the result is positive, the suspect is carted to a police station where a much more accurate machine is used to determine the blood alcohol levels. Only that ladt number is used as evidence.

I was assuming all countries had similar methods.

Re:Why does this need to be computerized?

[hey!]

The issue isn't with the software per se, but what the examination of the software revealed about the units as a system. If you used op amps instead of microcontrollers most of those issues would still be there.

The sensors used are temperature sensitive. The configuration used by the police disabled ambient temperature checks, which I guess you could call a digital issue. The device lacks a breath temperature sensor, which means that people with warmer than average breath could get false positives.

These devices also should be re-calibrated after a fixed number of uses; instead the state was re-calibrating them on a fixed schedule. While that schedule might work for an *average* device, devices that had been heavily could b e giving spurious readings.

On the flip side the device uses two different types of sensors to measure alcohol, and rejects readings where the sensors give different answers. This might mitigate some of the defects in how the state used them, but nobody can be sure. All we have is the assurance of the state authorities that the devices "have been tested to meet our business needs," without any specifics about what the test entailed.

The danger of these things is that they give you a number and it all seems so scientific and precise. You don't get the hemming and hawing that comes with a human opinion, metadata that helps you decide how certain you should be of that opinion. Layman don't understand the limitations of technology, they assume the tech should "just work". I'd trust a sophomore engineering student to devise policy for using these things over a police chief with decades of law enforcement experience.