Current Events > Researchers say a breathalyzer has flaws, casting doubt on countless convictions

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https://www.zdnet.com/article/draeger-breathalyzer-breath-test-convictions/

Exclusive: Two researchers say a police breathalyzer, used across the US, can produce incorrect breath test results, but their work came to a halt after legal pressure from the manufacturer.

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.

The two distributed their early findings to attendees at a conference for defense lawyers, which Draeger said was in violation of a court-signed protective order the experts had agreed to, and the company threatened to sue.

Their research was left unfinished, and a final report was never completed.

Draeger said in a statement the company was protecting its source code and intellectual property, not muzzling research.
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In order to produce a result, the Alcotest 9510 uses two sensors to measure alcohol content in a breath sample: An infrared beam that measures how much light goes through the breath, and a fuel cell that measures the electrical current of the sample. The results should be about the same and within a small margin of error -- usually within a thousandth of a decimal point. If the results are too far apart, the test will be rejected.

But the report said that under some conditions the breathalyzer can return an inflated reading -- a result that could also push a person over the legal limit.

One attorney, who read the report, said they believed the report showed the breathalyzer "tipped the scales" in favor of prosecutors, and against drivers.

One section in the report raised issue with a lack of adjustment of a person's breath temperature.

Breath temperature can fluctuate throughout the day, but, according to the report, can also wildly change the results of an alcohol breath test. Without correction, a single digit over a normal breath temperature of 34 degrees centigrade can inflate the results by six percent -- enough to push a person over the limit.