The evidence in question came from roadside drug tests, which are used to determine if a substance is illegal. The drug tests costs about $2 each and are convenient for police officers, which has led to an increase in use. The drug test solution is supposed to turn a different color if it is mixed with an illicit substance, but the test can result in false positives, which was the case in Nevada. Five people in Oregon and more than 250 in Texas also had their convictions overturned on similar grounds.
Officers often destroy the drug tests after a defendant pleads guilty to a drug charge, but a lab was able to analyze the tests in the above cases and render an analysis that resulted in exoneration of the suspects. Given the unreliability of the roadside drug tests, many judges will not allow prosecutors to introduce test results into evidence at trial, but officers continue to utilize them anyway.
The above examples illustrate why it is important to have a good criminal defense attorney before entering into a plea deal with prosecutors. An attorney is more likely to be aware of what evidence is inadmissible, and an attorney can decide if it is necessary to file a motion to suppress evidence if it was obtained illegally.