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Researchers warn police breathalyzer 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.

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