Nail Testing – When is it Useful?

Hair Strand Testing (HST) is the most widely used method for monitoring drugs and alcohol use in family law cases. However, when HST alone cannot provide a complete picture, nail testing offers a valuable additional perspective.

Nail testing is a reliable toxicological method that can detect drug or alcohol use or abstinence over a longer timeframe: up to six months for fingernails and up to 12 months for toenails.

Below we explain when nail testing is worth considering alongside HST to complement analysis.

Nail Testing vs Hair Testing: Key Differences

• Timing of Use Detection

Nail testing can confirm whether a substance was used but cannot indicate trends over time when they were used.  In contrast, hair testing can provide segmented results showing patterns of use over time, which can be helpful for identifying increasing or decreasing substance use.

• No Racial or Hair Colour Bias

Nail testing does not have a racial or hair colour bias in the same way hair strand testing can. Different people incorporate drugs into the hair at different rates over time and factors like hair colour, hair styling preferences or environmental contamination can alter the level of drugs found in a test and provide misleading picture of their consumption patterns.

• No Cut-Off Threshold for Nails

Many forensic testing companies use Society of Hair Testing (SoHT) cut-off levels when reporting hair test results, which can be misleading. FTS has explained why it never uses SoHT cut-off levels in its expert reports. We explain this issue in greater depth in our recently published articles:

• Why we think cut-off levels are inappropriate for the family courts
• Use of cut-off levels: the wellbeing of families hangs in the balance

Nail tests are not subject to these cut-offs, allowing for more comprehensive reporting and interpretation.

When to Use Nail Testing

• There is Limited or No Hair Available

For clients who are bald, have very short hair or who have insufficient or no body hair, nail testing offers a practical and non-invasive alternative.

• An Extended Detection Window is Needed

Nails grow more slowly than hair (about 3 mm/month for fingernails and about 1.0-1.5mm/month for toenails vs. 1.2 cm/month for hair), which allows for a longer retrospective detection window, up to 12 months. This is especially useful in cases requiring long-term substance use assessment.

• There is Risk of Environmental Contamination

Hair is more susceptible to external contamination, particularly in shared living environments where contact with substances may produce false positives. Nail testing is less affected by such exposure.

• Client has Cosmetic Hair Treatments

Hair treatments like dyeing, bleaching, or perming can affect test reliability. Nails are not commonly subject to cosmetic alterations, making them less prone to such interference.

• There are Disputed Hair Test Results

In cases where HST results are challenged, especially results based off the SoHT’s unhelpful guideline cut-offs, having a nail sample tested can provide critical clarity. One barrister successfully prevented a forced adoption by using a nail test to demonstrate abstinence, contradicting a contested hair test result.

How Nail Samples Are Collected

One of our trained collectors will take a nail clipping at the same time as the hair sample. Using sharp, sterile clippers, they’ll trim from the end of each fingernail or toenail. The process is quick, non-invasive, and completely painless, comparable to trimming your own nails at home.

Supporting the Courts with Reliable, Balanced Evidence

In short, no single test can provide the full picture in forensic toxicology.

Given the high stakes in family court cases, it’s essential to obtain as accurate and complete an understanding as possible. Combining hair and nail testing, together with a full forensic history from the client, offers a scientifically sound approach to assessing long-term substance use.

FTS recommends:

• Hair + Nail Testing: For a reliable overview of long-term substance use.
• Blood (PEth) + Urine (EtG) Testing: To assess recent alcohol consumption.
• A full forensic history from the client, which can help with interpreting results.

With this comprehensive testing strategy, FTS ensures our clients, and the courts receive balanced, robust, and defensible evidence.

For more information or to request a quote, contact the FTS Customer Service Team:
01924 480272
expert@forensic-testing.co.uk