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Hair Analysis in Forensic Toxicology

Tue, 09/03/2013 – 3:59am1 Comment

by Dr. Lata Gautam and Prof Michael D C

 

Forensic testing for drugs of abuse in hair has become a useful diagnostic tool in determining recent past drug use as well as examining long-term drug history through segmental analysis. The usefulness of hair analysis depends on the ability to identify and quantify drugs and metabolites in hair that arise from ingestion but not from passive exposure or exogenous application of drugs.Forensic testing for drugs of abuse in hair has become a useful diagnostic tool in determining recent past drug use as well as examining long-term drug history through segmental analysis (i.e. identification and quantification of drugs along the length of the hair shaft from scalp hair). The usefulness and the importance of hair analysis depends on the ability to identify and quantify drugs and metabolites in hair that arise from ingestion but not from passive exposure or exogenous application of drugs.

Hair is a unique matrix because no active metabolism or excretion occurs within its structure to remove drugs once they have been deposited. As a forensic science sample, hair has many beneficial aspects when compared to urine and blood. Since sample collection is non-invasive, hair analysis is commonly used in workplace drug testing and drug treatment programs. Provided the hair has not been cut, it may be easy to obtain a second sample if the results are inconclusive or challengeable. It can be used for establishing personal drug history in situations where classical matrices are not available such as in putrefied bodies; when the full drug use history is unknown; or when time is a factor, for example in drug facilitated sexual offense (DFSA). Hair analysis can also assist in drug compliance testing and drug abstinence monitoring. Moreover, drug-hair analysis is becoming a popular alternative to urinalysis since urine samples provide only short-term information about drug use while hair samples provide a larger window of detection as well as history of use over time. This is because head hair grows at an average rate of 1 cm per month and hence preserves the drug use history of an individual along its length. Due to the cosmetic treatment of an individual, the drugs could be degraded however not fully eliminated. Therefore cosmetic history of a person must be considered in such cases while interpreting hair analysis results.

Cases of Hair Analysis
The first case of the determination of poison in human hair was published in the 1850s and reported the presence of arsenic in the hair of a body exhumed after 11 years. After almost 100 years, in 1954, the detection of barbiturate in an animal model study (guinea pig hair) was reported. Since then, much of the literature has been published on drug-hair analysis and great interest has been shown in this matrix as an alternative and complementary specimen. The usual analytical approach includes a screening test by immunoassay followed by confirmation of positive results using both gas or liquid chromatography (GC or LC) coupled with mass spectrometry (MS) such as GC-MS, GC-MS/MS, LC-MS, LC-MS/MS. The Society of Hair Testing (SoHT) recommends that the confirmation technique should include the detection of a parent drug and metabolite(s) so that the presence of drugs due to passive exposure can be differentiated from ingestion.¹

Hair has been used as an alternative and complementary matrix in a number of cases; such as a case of accidental cocaine poisoning² and a case of drug addiction.³ A 25-year-old man unknowingly consumed an entire bottle of an imported Columbian soft drink (Pony Malta) that contained smuggled cocaine in it. The man was hospitalized for acute cocaine intoxication but died 24 days later. The blood sample on his hospital admission contained 2.3 mg/L of cocaine and 4.5 mg/L of benzoylecgonine, whereas the segmental analysis of hair from the autopsy sample revealed a peak cocaine concentration in the segment corresponding to the time he ingested the tainted beverages.²

In another case, the addiction history of a dead woman was evaluated after exhumation and sectional hair testing. The post-mortem blood and urine analysis confirmed recent opiate and cannabis use and indicated that her death was associated with heroin abuse. Several months later, the woman’s family asked for exhumation and re-examination of the body, insisting that the cause of death was homicide. The drug profile in the hair shaft was investigated by segmental analysis which revealed that the total morphine concentration in the hair sections corresponding to the three month period before death were significantly lower than those of the four to ten month period before death. Therefore, the cause of death could have been the decrease of tolerance to heroin caused by abstinence and relapse in use.³

Other evidence of drug-hair analysis cited in the literature include a fatal case involving polydrug use (heroin, cocaine, cannabis, chloroform, thiopental, and ketamine); evidence of gestational heroin exposure by comparative analysis of fetal and maternal body fluids, tissues and hair; and intrauterine drug exposure during second trimester of pregnancy in a heroin-associated death. Recently emerged drugs such as piperazines, cathinones, and synthetic cannabinoids have also been detected in hair. Simultaneous detection methods have been developed to analyze different classes of drugs (opiates, amphetamines, cocaine and metabolites, diazepam and metabolite) from a single extraction method which makes it suitable for general toxicology screening.⁴

There are some issues that need to be considered while using hair analysis as an alternative and complementary matrix for forensic drug testing. The external presence of drugs in hair via passive exposure should be taken into account during the sample preparation and evaluation of results. Similarly cosmetic treatments and the presence of endogenous compounds such as GHB and cortisol can affect the concentration of drug detected in hair and hence care should be taken while interpreting such results. In this regard, SoHT has published internationally accepted guidelines.¹ This provides step-by-step guidance for hair analysis, including sample collection, storage, preparation, pre-treatment, analysis, and the use of cut-offs in order to enable identification of chronic drug use. Cut-offs for chronic alcohol use have been discussed in the Society’s consensus documents as hair is also analyzed to detect alcohol. SoHT also runs a proficiency testing program annually and there are two other such schemes available in Europe: a) HAIRVEQ established by the Istituto Superiore di Sanità of Rome in Italy, in cooperation with Institut Municipal d’Investigaciò Mèdica of Barcelona in Spain; and b) GTFCh set up by the German Society of Toxicological and Forensic Chemistry. SoHT recommends that segmental analysis should be carried out when the analyte is endogenously present such as GHB and cortisol. This is because these compounds should be detected at an elevated level at the time corresponding with exposure.

Conclusion
Hair samples are useful as a matrix for drug testing because drugs can be detected for longer periods than in blood or urine or other biological samples. The use of hair analysis as an adjunct to traditional samples may help document drug use history and is especially useful in situations when blood and urine specimens have not been collected on time. The drug screening of hair as an alternative and complementary matrix provides important information in various drug-related investigations, including DFSA, patient compliance, and gestational exposure. It is recommended to collect hair samples in all cases for later analysis if warranted by additional history or autopsy findings. Method accreditation is challenging due to limited availability of certified reference materials to be used as external quality controls and hence participation of hair testing laboratories in proficiency testing programs is highly recommended.

 

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