https://www.nytimes.com/2019/11/03/business/drunk-driving-breathalyzer.html (https://www.nytimes.com/2019/11/03/business/drunk-driving-breathalyzer.html)
Alcohol breath tests, a linchpin of the criminal justice system, are often unreliable, a Times investigation found.
Used to work for Dräger calibrating and maintaining the breathalyzer units for police, and indeed they need to be calibrated often or you will get skewed results