False Positives in Drug Field Testing Kits

The director of a lab recognized by the International Association of Chiefs of Police for forensic science excellence has called field drug testing kits “totally useless” due to the possibility of false positives. In laboratory experiments, at least two brands of field testing kits have been shown to produce false positives in tests of Mucinex, chocolate, aspirin, chocolate, and oregano. However, law enforcement agencies continue to employ these kits.

Fox 13 Tampa investigated the validity of drug field testing kits in the wake of arrests of three people based on false positives from field tests. Eventually all three were cleared and all charges were dropped. However, for the months between arrest and confirmatory testing by the state crime lab, the individuals felt that they were “guilty until proven innocent.”

Dr. Omar Bagasra, a research scientist at Claflin University, has been looking into the validity of field drug testing kits. In controlled tests in his laboratory, Dr. Bagasra, Dr. Cherilyn Haggen-Paey, and forensic scientist Chris Addanki, have demonstrated that the chemicals used in the kits are prone to give false positives even with common household materials. According to their tests, Mucinex can produce false positives for heroin and morphine; chocolate can be interpreted as marijuana; and soap can test positive as GHB. Even exposure to air caused false positives in some kits, according to their tests. The scientists noted that they had trouble interpreting results in a laboratory environment and “you can imagine in the field it’s even more difficult.” However, the experts say the problems are not linked to just the individual kits tested or a specific manufacturer, as many the field test kits tend to contain the same chemicals.

Field drug testing kits were created to screen for illicit substances in the field followed by more complete testing in a laboratory setting. However, the tests stand in for more scientifically valid testing until analysis at state crime labs occurs. Drug testing at state crime labs is typically performed just prior to trial due to the high rate of plea bargaining in drug cases, and therefore false positives are often not discovered unless contested at trial. During this time, the false positives from field tests can cause innocent citizens to be detained in jail for weeks or even months.

“False Positive Equal False Justice,” a 2008 report created for the California Attorneys for Criminal Justice, noted that false positives resulting in criminal charges has been an ongoing problem. In 2003, a Pennsylvania college student was held for three weeks when flour was mistaken for cocaine. In 2007, musician Don Bolles was arrested for possession of GHB which was actually soap. Additionally the report lists approximately forty extracts—such as vanilla, peppermint, or ginkgo—which can test as false positives for marijuana.

Dr. Frederic Whitehurst, a Ph.D. chemist and former FBI lab supervisor, has expressed concern with the use of field drug testing kits. He stated that he has “no confidence at all in those test kits.” Due to the high chance of false positives, both Dr. Whitehurst and Dr. Bagasra have recommended that drug field testing kits not be used. They say law enforcement would receive more valid results by waiting for results from lab testing. The kits are single use and range from a $4 to $20 a use depending on what drug is being investigated.

For more general information on forensic drug analysis see https://forensicresources.org/forensic-disciplines/drug-analysis/

Click here to read an article about the 2011 arrest of a man in Buncombe County based on a false positive field test result of cheese and tortilla dough.