In recent years hair has become a fundamental biological specimen, alternative to the usual samples blood and urine, for drug testing in the fields of forensic toxicology, clinical toxicology and clinical chemistry. Moreover, hair-testing is now extensively used in workplace testing, as well as, on legal cases, historical research etc. This article reviews methodological and practical issues related to the application of hair as a biological indicator of drug use/abuse or of chronic exposure to environmental toxicants. Hair structure and the mechanisms of drug incorporation into it are commented. The usual preparation and extraction methods as well as the analytical techniques of hair samples are presented and commented on. The outcomes of hair analysis have been reviewed for the following categories: drugs of abuse (opiates, cocaine and related, amphetamines, cannabinoids), benzodiazepines, prescribed drugs, pesticides and organic pollutants, doping agents and other drugs or substances. Finally, the specific purpose of the hair testing is discussed along with the interpretation of hair analysis results regarding the limitations of the applied procedures.

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Accurate interpretation of the blood ethanol (EtOH) concentration at the time of death presents a difficult task since the origin of detected EtOH in postmortem cases (either in corpses or in specimens after sample collection) may vary. Headspace gas chromatography is the choice method for detecting EtOH in blood or other specimens, due to the accuracy and sensitivity it provides. Possible sources of postmortem EtOH have been the ante-mortem ingestion, the ante-mortem endogenous production and the postmortem microbial neo-formation, which has been considered the most critical factor that could complicate the results. It has been reported that EtOH could be formed postmortem in variable and non-predictable amounts, as a function of the type and number of microorganisms present either in corpses or specimens collected at autopsy. The presence of other volatiles-mostly n-propanol-has been correlated to microbial EtOH production, although the quantitative pattern between them and EtOH still remains obscure. The factors most frequently implicated in the mechanism of postmortem EtOH production in corpses have been considered the number and nature of microbes present, the availability of various types of substrates, the temperature and the time. Complication in the interpretation of blood alcohol concentration could arise due to the atypical distribution of EtOH in the body compartments after death. Specimens to blood EtOH ratios reported in the literature are presented. All the aforementioned aspects are discussed in a comprehensive way, providing a deep insight into this essential problem.

The most abundant volatiles detected during the forensic ethanol analysis are ethanol, acetaldehyde, 1-propanol, 2-propanol, and acetone. These volatiles could either be initiated in the human body after the consumption of alcoholic beverages; or have been produced ante mortem during metabolic processes or post-mortem by microbes. Aims of this study were the determination of the volatiles' concentrations in autopsy blood samples received from 483 routinely autopsied corpses and classification of their patterns according to the manner of death, and the presence of putrefaction at autopsy. The volatiles concentrations were determined by a validated gas chromatographic method. The experimental values obtained from these determinations were submitted to statistical evaluation by principal component analysis (PCA). Blood acetaldehyde, acetone, 1-and 2-propanol concentrations were higher in cases of violent and undetermined deaths compared to the ones determined in cases of natural deaths. Blood volatiles concentrations were dispersed in higher values in cases with putrefaction compared to cases without putrefaction at autopsy. Blood volatiles had low values in the majority of cases with low BAC. All volatiles had higher maximum concentrations and broader concentration ranges when BAC ranged from 10-100 mg/ dL. Cases of undetermined manner of death along with some cases of violent deaths achieved clustering (PCA) from cases of violent or natural manner of death indicating similarities among the grouped samples on the basis of measured blood 1-propanol and ethanol concentrations. The latter novel finding needs further investigation using a larger dataset pool and possibly other classification method with a different regression model.

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