Evidence shows that chemical field tests used for alcohol and drugs are unreliable because they often give false positive results. Many states and law enforcement officials are questioning the reliability of field tests to warrant arrests.
Chemical Field Tests
The use of chemical field tests to determine a level of an illegal substance in a person’s blood has been a longstanding practice in most states. Chemical field tests have been used by police departments across the country for decades. Officers drop a suspicious substance into a pouch of chemicals and use changes in color to determine results so they can make arrests for illegal drugs including marijuana, cocaine, heroin, and methamphetamine.
These cheap $2 chemical kits used to make roadside DWI and drug arrests have contributed to thousands of wrongful convictions over the years. Recent evidence shows that chemical field tests are unreliable and often give false positive results. In many cases, a DWI attorney sees innocent people who receive chemical field tests with false positives that are arrested and charged with a crime. Due to recent findings, many states and law enforcement officials now require that any positive field test is confirmed in a crime lab prior to an arrest. Because of so many false positive results and wrongful convictions, courts in most states now bar chemical field tests from being used as sole evidence in a criminal trial.
For many years, law enforcement and criminal prosecutors have held briefings to try to convince court judges that chemical field tests are reliable conviction tools. Kevin Burke, a Minnesota district court judge, stated that he is aware of this practice and has been in similar meetings during his 30 years on the bench. According to court records and interviews, these tactics have happened regularly over the years, when law enforcement and criminal prosecutors want to widen the use of the tests. The presenters attest to their accuracy and vouch for their usefulness. Mr. Burke stated that he has concerns that prosecutors may be lobbying judges, and to prevent wrongful convictions both prosecutors and defense attorneys should be present at such meetings.
Over the years, chemical field tests have been considered legitimate tools to determine the presence of illegal drugs and warrant an arrest. However, those studies have always shown that chemical field tests have questionable limits. Due to false-positive results that lead to convictions of innocent people, studies suggest that chemical field tests should not be used as sole evidence of illegal drugs in an arrest. According to federal guidelines, all drugs must be identified by a qualified crime lab to warrant an arrest in criminal cases.
Chemical Field Tests Convict Innocent People
Every year in the U.S., over 1.2 million people are arrested by police officers and charged with illegal drug possession due to the results of $2 roadside chemical field test kits. These kits have been proven to show unreliable, incorrect results, yet they have remained unchanged since 1973. Police officers rely on these kits because they are simple to use in vehicle stops where drug use is suspected, but the tests have proven to have a lot of things that can go wrong and interfere with accurate results.
A chemical field test kit usually contains one tube filled with a chemical, cobalt thiocyanate. When the chemical is exposed to cocaine, it turns blue. However, cobalt thiocyanate also turns blue when it’s exposed to methadone, some acne medications, and several common household cleaners, as well as about 80 other compounds. Some tests kits contain three tubes of chemicals which the police officer can open in a specific order to rule out all illegal substances except the drug in question. However, if the officer opens and uses the tubes in the wrong order, false positive results can occur. Other influences that can cause false positive results include:
- Temperatures – Cold temperatures slow down the color development in chemical test kits, while warm temperatures often prevent color reactions entirely. In a roadside vehicle stop, chemical field tests are especially vulnerable to errors caused by outdoor temperatures.
- Lighting – Roadside vehicle stops often include poor or no outdoor lighting, bright street lamps, sun glare, and flashing police lights. All of these factors interfere with fine distinctions in chemical color changes that can make the difference between an arrest and a release.
The manufacture of chemical field tests are not regulated by any supervising agency and no comprehensive records are kept about their use. There are no established error rates for field tests because their accuracy varies significantly based on who uses them. As a result, false positive test results contribute to arrests and convictions for drug offenses for countless innocent people who end up taking plea deals that land them in jail.