Speak with an expert today (424) 363-3347(For attorneys only)

How Accurate are Hair Follicle Drug Tests

forensic toxicology

Forensic Toxicology and False-Positive Hair Tests

Forensic toxicology is an established discipline with tried-and-tested methods for detecting chemicals, drugs, and toxins. As scientists, we pride ourselves on delivering accurate results.

Unfortunately, sometimes mistakes do slip by us. In these cases, the best thing to do is learn from the mistake and improve our procedures.

Recently, the Institute of Forensic Medicine in Germany released a study showing that hair follicle drug tests can sometimes show a false-positive – particularly when testing for marijuana. With this in mind, we have to ask how accurate hair follicle tests are.

How Does Hair Follicle Testing Work?
As your hair grows from the follicle, chemicals in your blood stream are deposited in the strand of hair. This includes a number of toxins, as well as legal and illegal drugs. Because most people’s hair grows at a steady rate – about half an inch each month – one strand can provide a timeline of the test subject’s consumption of various substances.

In forensic toxicology, we segment the hair – basically dividing it into month-long time periods – and test each section for illicit chemicals.

Is It Reliable?
Most companies that require their employees to be drug tested opt for urine testing. It’s the cheapest and easiest method for mass testing. With dipstick tests, preliminary drug screening is also instantaneous. However, urine samples can only show drugs that have been the subject’s system in the last 3 days. There are also a few ways to cheat urine tests, like substituting someone else’s urine or using synthetic urine.

Hair follicle testing is more expensive and time consuming, but also gives a longer window of detection and is more accurate in measuring long-term low-level drug use. It’s also difficult to fake a hair sample, as the sample can be taken in front of a witness. All in all, hair testing is more reliable and thorough than urine testing.

So What’s the Controversy?
The study from the Institute of Forensic Medicine argues that false positives are possible, as the hair might be contaminated from an outside source. For example, if you are in close contact with someone who smokes marijuana, your hair might absorb small traces of THC from second-hand smoke, or from the marijuana-user touching your hair.

When we perform toxicological hair analysis, we are meant to test for molecules present inside the hair shaft. This is supposed to negate any external contaminants from invalidating the tests.

We should also be testing for THC-COOH, not THC. Tetrahydrocannabinol (THC) is the psychoactive chemical in marijuana that gets you high. THC-COOH, on the other hand, is a metabolite formed by the body when THC is consumed. However, some studies show that in cases of extreme exposure to second-hand smoke, even non-smokers can test positive for THC-COOH in urine tests. These cases are rare, but at this time it’s not clear if the same problem applies to hair follicle testing.

More Rigor Needed
As it stands, this particular study only looked at detecting false-positives for marijuana. In other cases where hair tests show false-positives for other drugs, this is probably down to sloppy lab work and human error.

Instead of abandoning hair follicle testing altogether, forensic toxicologists need to conduct further studies, and develop more rigorous standards for testing.

Spread the love


Lawyers of Distinction USFCR Verified Vendor

Recent Blog Articles

The Process Of Analyzing Data In Forensic Toxicology

Forensic toxicology is a complex field revolving around the use of toxins, chemicals, and poisons, particularly pertaining to instances of crime or even death. It is important to understand the role that data can play in the outcomes of court cases where forensic toxicology comes into play. Understanding Data In…

Spread the love

Read More

When To Hire An Expert Witness

In the simplest terms, an expert witness is a person who testifies in a trial because of their vast knowledge in a subject or field that is pertinent to the case. There are only five significant categories of expert witnesses: financial, forensic, medical, mental health, and vocational. However, within each…

Spread the love

Read More

What Are Your Rights With DUI Testing?

The law against drinking and driving is a hard and fast rule. But the rules are a little less clear when it comes to DUI testing. Police officers administer various types of drug tests across the country’s roads on a regular basis, but do these people know their rights when…

Spread the love

Read More

Speak with an expert today!

Contact the offices of Okorie Okorocha for professional and reliable advice which you can trust.

Call (800) 285-1763 Contact Us