How Effective Are Hair Follicle Tests in Detecting Drug Use?


Both law enforcement agencies and probation officers may utilize drug testing for various reasons. Police officers may obtain warrants for tests to support charges for DWI or similar offenses. When people are placed on community supervision, especially for crimes involving illegal substances, they often are subject to random drug testing. Drug courts or pretrial diversion programs also may require random drug testing as a condition of participation. As a result, individuals may have to undergo hair follicle testing when they become involved in the criminal justice system.

Hair follicle testing may be one of the most effective means of detecting drug use in individuals. While probation officers and others traditionally used urine testing to identify the use of drugs in people on community supervision, hair follicle testing likely is more accurate at targeting drug use. Urine tests will not reveal signs of drug use if it has been two or three days or more since the person last used drugs. In contrast, a hair follicle test can show drug use over a much more extended period. Each ½ inch of hair can reveal drug use within 30 days. The standard hairs used in hair follicle tests are one and one-half (1 1/2) inches long, which can show if the person used drugs at any time within the last 90 days.

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How Effective Are Hair Follicle Tests in Detecting Drug Use?

Labs that perform hair follicle testing generally use hairs taken from the scalp, but they still can perform the tests on body hairs, as well. Bleach, hair coloring, shampoos, and external contaminants such as smoke have no impact on the results of the hair follicle testing.

Hair follicle testing can detect all types of illicit drugs, including marijuana, amphetamines, cocaine, opiates such as heroin, and PCP. False positives are possible in some instances, usually from consuming certain foods containing specific compounds. As a result, a second screening test occurs to rule out false-positive test results.

When you are facing any criminal charges in the State of Texas, you need an experienced criminal defense attorney to represent your interests. Contact Peek Law Group at  (512) 399-2311 today and set up an appointment to speak with our legal team.

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