An investigation has found that the portable breath tests used nationwide in DWI stops are frequently not reliable, reports the New York Times. These tests produce distorted readings at an “alarming” rate for a variety of reasons, including improper calibration, major software errors, and police departments choosing less trustworthy machines to begin with. Despite problems like this, PBTs are so prevalent that each state has laws that sanction the refusal of this test. But the Times reports that more states are becoming aware of unreliable PBT testing. For instance, a Minnesota judge ruled in 2018 that PBTs were apparently giving rounded-up readings.