Ongoing challenges and recent court cases have highlighted some persistent flaws with DUI breathalyzer tests. The device itself can be faulty, particularly when it has not been regularly calibrated and tested, or the officer may not administer the test correctly due to a lack of training. Environmental factors, like extreme temperatures, can potentially skew the results of a breathalyzer test, as can the presence of residual mouth alcohol from certain foods, drinks, or even mouthwash.
Manufacturers have consistently refused to disclose the source code for their breathalyzer software, so full scientific scrutiny regarding how the results are calculated has been elusive. In a 2025 Minnesota case, a judge ordered the disclosure of source code for an Intoxilyzer 5000, citing the “enormous” potential for errors resulting from the unproven methodology of the device. Since breath samples are not preserved, the machine essentially validates its own “secretive analysis.”