The tail in the nail or ponytail

by Julie Evans

Advances in science make detection of a person's drug history through analysis of hair or nail samples a real possibility

The Journal, August 2007, page 42

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Have you ever wished you could look at a person’s drug lifestyle, or that drug use could be detected more than a few days later? Well, you can.

Drugs, chemicals and biological substances when ingested, smoked or otherwise permitted entry to the body, enter the bloodstream. Circulating round the body, they can become incorporated into keratinised matrices such as hair and nails. The slow growth rate of these matrices and the persistence of chemicals within them afford an opportunity to investigate an individual’s lifestyle.

Hair today…

Drug testing in hair has been around since the 1960s. However, the early testing could only be used to investigate prolonged exposure to metals such as arsenic and lead. Technological advances resulted in the first scientific paper on drug detection in hair being published in 1979. During the 1980s familiarisation with techniques, and increasing interest, resulted in increased research, but still essentially limited to a small group of commonly abused drugs, and only detecting regular use.
From the late 1990s, continued improvement in sensitivity of methods resulted in a single exposure to many drugs becoming detectable.
To date, much of the research has centred on hair. However, this matrix is not without its problems. Its ability to incorporate drugs is influenced greatly by colour. As a general guide, the darker the natural hair colour, the better the hair is at binding drugs to it.
A further drawback is that chemical treatment of hair can result in loss of a high proportion of any drug content. In an age where many people frequently bleach, perm or dye their hair, this can be a considerable limitation on the evidential value of hair analysis. There is then, of course, the problem of those with little or no hair.

Nails: growing interest

In response to these problems the use of nails was considered as an alternative medium for testing. As another keratinised matrix, it would be expected to incorporate drugs. As with hair, drugs can be lost from nails through washing and can be incorporated from the environment. However, nails are not normally subject to aggressive chemical treatments and they are available in most of the population. With interest aroused, work was done to investigate drug incorporation into nails and they have proved another means to assess a person’s drug exposure or use.

Currently there is a paucity of data on expected drug concentrations in nails, but they do provide an extended window of drug detection, permitting patterns of exposure to be investigated even if the extent of use cannot be determined.

For obvious reasons, in the living only nail clippings can be used and growth rates are difficult to predict. Nevertheless, nails do offer a viable alternative where the suitability or availability of hair gives concern. In the deceased a whole nail can be obtained providing several months of history.

Benefits in practice

The advantages of both keratinised matrices over traditional drug testing methodologies employing body fluids, such as urine or serum, include:

• non-invasive collection procedure;
• longer window of detection: a record spanning several months is possible;
• greater stability of sample;
• convenient shipping and storage
• (no need to refrigerate);
• more difficult to adulterate samples;
• they can demonstrate patterns of exposure.

Cases where this type of testing has proved useful include:

• child custody, to demonstrate that a parent/carer abuses drugs, or is adhering to a withdrawal programme;
• child protection, to assess whether a child is exposed to drugs in the home;
• a drug-facilitated sexual assault not reported until some days later, when the opportunity for blood and urine testing has passed;
• possession with intent to supply controlled drugs, to assess whether the person was a user and thus support or refute a claim that drugs found were for personal use;
• workplace and pre-employment testing;
• any situation where lifestyle might be of interest or an indication is required of whether a drug had been used on a single occasion or more frequently.

There are limitations to this testing. Hair and nails won’t give precise information on when drugs were taken, or the amounts taken. As such they will never replace blood or urine in investigating crime. They do, however, provide a means to assess whether they have been taken and whether that use was as a one-off or on multiple occasions, and thus their analysis compliments the traditional matrices. There has been a great deal more research done on drugs in hair than in nails and, for the present, a hair sample taken correctly would be the first choice. However, where hair cannot be taken, or where there are concerns about contamination or chemical treatment, nails can provide some valuable information.

Julie Evans, Forensic Toxicology Service Director, Eurofins Forensic Services, 318 Worple Road, Raynes Park, London SW20 8QU?

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DRUG TRACER: creating a use history

Drugs, chemicals and biological substances which enter the bloodstream, can become incorporated into keratinised matrices such as hair and nails, forming a record like a little tape recording of drug use. Scientific techniques can now detect a single exposure to many drugs, though problems remain

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