Police officers in New York have made the news many times for questionable practices, but a few other states took the spotlight in a recent news story about roadside drug testing. In Nevada, prosecutors overturned five drug charge convictions after a lab determined that a substance believed to be cocaine was not, in fact, an illegal substance at all. The convictions were overturned in 2017, but the district attorney’s office only disclosed this to the National Registry of Exonerations this year.

The five convictions overturned resulted from guilty pleas, which the defendants entered into after police told them that a substance found on their persons tested positive for cocaine. Police made this determination after using a roadside drug test, which is done by combining a sample of the substance in question with a liquid. The liquid is supposed to turn a particular color, depending on what the substance is.

Though the roadside drug tests have been said to be reliable enough to establish probable cause for an arrest, many judges will not allow these tests into evidence at trial given their unreliability. Officers seem to like the tests because they are quick and cheap, but Clark County was not the first place that had to overturn convictions after the tests resulted in false positives. Five similar drug charge convictions were overturned in a county in Oregon, and over 250 were reversed in Houston.

Despite the inaccuracy of these tests, prosecutors can rely on them to coax a confession or a guilty plea out of a defendant facing drug charges. To make matters worse, police officers sometimes destroy the roadside tests after a defendant pleads guilty. These reports of wrongful convictions help emphasize the importance of consulting with a criminal defense attorney before speaking with an officer or prosecutor.