Violations can occur from a driver not having reached the "zero tolerance" level, but can also occur from use by other drivers within legal limits, or from test anomalies. In some states, anomalies are routinely discounted, for example as not consistent with patterns of BAC levels or at levels incompatible with life (e.g., significant mouth alcohol - if read as BAC would mean the patient is dead). In some states, "fail" readings inconsistent with actual alcohol use can be cleared by a routine process, but other states automatically deem these "fail" readings as violations.