Understanding Hair Strand Testing in Family Court

Legally reviewed by: Ravi Kaur Mahey Sep 2026 In: Child Care

In family law cases in England and Wales, where substance use or child welfare is in question, hair strand testing (HST) is often requested by social services or directed by the court. It is one of the primary indicators of previous drug and alcohol patterns over time.

This guide helps understand why hair strand testing is used, how the process works and how different factors can impact test results.

What is Hair Strand Testing?

A hair strand test checks if you have used drugs or alcohol over the past 3 to 12 months.

When you use drugs or alcohol, your body breaks them down. These tiny markers travel through your blood and get trapped inside your hair as it grows. They stay inside your hair until it is cut or falls out.

To do the test, a collector cuts a small segment of hair from the back of your head, just above the scalp.

Why Does the Court Choose Hair Testing?

Family courts usually don’t use methods such as urine testing, nail testing or body hair testing. These methods do not show substance use history like hair strand testing and methods like urine testing may only show results of up to 2 or 3 days. If someone stops using drugs for just three days, a urine test will come back clean, even if they use drugs heavily at other times.

Head hair acts as a timeline. Every 1cm of hair represents one month, due to its rate of growth. This means it can be cut into 1cm pieces to show month-by-month trends.

How Lab Differences Can Impact Your Case

Not all hair strand tests are carried out or processed in the same way. Depending on which lab tests your sample, the results given to the court can look very different.

Overview vs. Month-by-month: In an overview, the lab tests a hair sample all at once to give a single average result across the whole timeframe. A segmented test cuts the sample down into 1cm pieces and can be used to show the court that you have stopped or reduced substance use over a monthly timeline.

Secondhand Exposure: If you are in a room where other people are smoking cannabis or using drugs, drug dust can land on the outside of your hair. A basic lab test may see this and automatically classify your test as positive. A specialist forensic lab uses special washing techniques to separate any surface dust from what is actually inside your hair. This helps prevent you from getting a false positive test from passive exposure to other people’s drug use.

How is the Sample Collected?

A hair strand test usually takes place in a professional environment such as a clinic, a lab or a hospital. A trained professional will collect three samples:

Primary Sample: A small lock of hair taken from close to the scalp. Usually the thickness of a pencil.
Control Sample: A second lock of hair is taken at the same time. This is kept in case you or your solicitor want a second opinion or to re-test the results later on.
Environmental Swab: The lab or a collector wipes hands or surfaces, to check if any drugs were floating around in the air rather than inside your body. The lab will use special washing steps on the hair itself to check whether drugs were present in the surrounding environment, rather than personal use.

Can You Bleach, Dye or Cut Your Hair Before the Test?

Individuals may believe that they can ‘cheat’ a hair strand test if they cut, dye or bleach their hair. However, this can have legal consequences.

Chemical bleaching or dyeing of the hair breaks down the outer layer of the hair. While this can lower levels of the drug markers, it almost never gets rid of all of them. If you dye or bleach your hair right before a test, the judge might think you were trying to hide something.

The court can see cutting or shaving your hair as refusing to co-operate or trying to destroy evidence. They will simply order a nail or body hair test instead.

Hair Structure and Racial Differences

One issue with HST is that not all hair is the same.

Dark hair traps more drug markers: Dark brown or black hair contains more melanin, a natural pigment in your body. Drugs stick very strongly to dark melanin. This can cause unfair test results, as someone with dark hair is more likely to show a high positive result than someone with light blonde hair, even if their drug use was lower or the same.

Afro-textured hair and hair products: Afro-textured hair has a unique structure. It is also naturally drier and people often use hair oils, creams or gels to maintain it. These products can stick to the hair and make it harder for a lab to remove any surface dust or smoke.

Using heated tools regularly: Using hair straighteners or curlers can change the outer layer of the hair. This makes it easier for drug dust or smoke to get into the hair.

These differences can mean a simple positive number is not always the full story. If you have dark or afro-textured hair, or use heat or hair products on your hair, your solicitor can ask a forensic specialist to review your results, ensuring your hair colour, hair type, and hair care routine are taken into full account.

If you need legal advice on hair strand testing and what this involves, speak to one of our Family Law team today.

Frequently Asked Questions

What if I use prescription medications or over-the-counter drugs?

Certain prescription medicines, pain relievers, and even some over-the-counter cough syrups can show up on a hair strand test. You should notify your sample collector of all the medications you have taken recently, and bring evidence of this.

Can hair extensions or weaves affect my test?

Yes, they can because the lab need your natural hair connected to your scalp. If you have extensions or a weave, the collector may carefully isolate your real hair, or collect hair from your body.

Can everyday items like shampoo, hair oil, or swimming pool chlorine alter my results?

Everyday washing with shampoo will not strip the drug markers in your hair. However, using clarifying shampoos or swimming in chlorinated pools regularly can weaken the outer layer of the hair. This can cause slight washing out of internal drug markers.

Who pays for the hair strand test in family court?

The cost of the test is usually funded through Legal Aid, in family court cases involving social services or local councils. Or it is shared between the parties involved. Your solicitor can apply for funding or inform the court about who is responsible for covering the laboratory fees.

What if I refuse to do the hair strand test?

Refusing a test is not a criminal offence, but if you refuse, the judge is allowed to draw an adverse inference. This means they assume you refused the test because it would have come back positive.