Critical analysis of forensic cut-offs and legal thresholds: A coherent approach to inference and decision

A probabilistic approach to evaluate salivary microbiome in forensic science when the Defense says: `It is my twin brother'

Salivary microbiota profiles may represent a valid contribution to forensic investigation when standard DNA genotyping methods fail. Starting from questioned and control materials in the form of saliva, the evidence can be expressed by means of a distance between those materials taking into account specific aspects of the microbiota composition. The value of the evidence for forensic discrimination purposes is quantified by means of a Bayes' factor, that allows one to overcome the major limitations and pitfalls of intuition connected to the use of cut-off values as a mean of decision.

Accelerated Extraction and Analysis of Ethyl Glucuronide in Hair by Means of Pressurized Liquid Extraction Followed by Liquid Chromatography-Tandem Mass Spectrometry Determination

The measurement of ethyl glucuronide (EtG) in hair is an established practice to evaluate alcohol consumption habits of the donors; nevertheless, analytical variability has shown to be an important factor to be considered: measured EtG values can vary significantly as a consequence of analyte washout during decontamination, pulverization of samples, extraction solvent and incubation temperature. In the present study, we described a new method for automated hair decontamination and EtG extraction from the inner core of the hair by using pressurized liquid extraction (PLE), followed by solid-phase extraction (SPE) cleanup; validation was performed according to SWGTOX guidelines. The extraction efficiency of the new method was evaluated by comparing the results with those obtained by a validated and ISO/IEC 17025:2005 accredited method; an average positive difference of + 32% was observed when the extraction was performed by PLE. The effect of hair pulverization was also studied, and a good correlation between cut and milled hair was observed, implying that PLE allowed a highly efficient extraction of EtG from the inner keratin core of the hair, no matter if it has been cut or pulverized. Finally, to verify the results, paired aliquots of 27 real hair samples were analyzed with both PLE and a protocol optimized by design-of-experiment strategies planned to maximize the extraction yield; in this case, a comparable efficiency was observed, suggesting that exhaustive EtG extraction was obtained with both approaches. This finding opens new perspectives in the eligible protocols devoted to hair EtG analysis, in terms of speed, automation and reproducibility.

Minor or adult? Introducing decision analysis in forensic age estimation

Nowadays, forensic age estimation takes an important role in worldwide forensic and medico-legal institutes that are solicited by judicial or administrative authorities for providing an expert report on the age of individuals. The authorities' ultimate issue of interest is often the probability that the person is younger or older than a given age threshold, which is usually the age of majority. Such information is fundamental for deciding whether a person being judged falls under the legal category of an adult. This is a decision that may have important consequences for the individual, depending on the legal framework in which the decision is made. The aim of this paper is to introduce a normative approach for assisting the authority in the decision-making process given knowledge from available findings reported by means of probabilities. The normative approach proposed here has been acknowledged in the forensic framework, and represents a promising structure for reasoning that can support the decision-making process in forensic age estimation. The paper introduces the fundamental elements of decision theory applied to the specific case of age estimation, and provides some examples to illustrate its practical application.

Interpol review of glass and paint evidence 2016-2019

This review paper covers the forensic-relevant literature in paint and glass evidence from 2016 to 2019 as a part of the 19th Interpol International Forensic Science Managers Symposium. The review papers are also available at the Interpol website at: https://www.interpol.int/content/download/14458/file/Interpol%20Review%20Papers%202019.pdf.

Detection of cocaine on euro banknotes; Development of a practical approach for the interpretation of suspect cases

The presence of traces of narcotics, particularly cocaine, on banknotes in circulation is a known and widespread fact in all countries. While linked to consumption and trafficking (primary contamination), their spread is due to direct contact with other banknotes during machine counting and cash financial transactions. The mere detection of traces of cocaine on a sample of banknotes is therefore not sufficient evidence to establish the banknote's illegal origin. Increasing levels of contamination are recorded close to (in terms of both place and time) the first direct contact with the substance. The analysis must thus be able to demonstrate that the concentration of narcotics on the banknotes is significantly higher (statistically) in terms of value and frequency than would be expected from background noise alone. Even in that event, however, this evidence has to be substantiated with additional confirmations linking banknotes to the person and this latter to drug trafficking and/or dealing. In general, an in-depth and systematic analysis of all seized banknotes to search for traces of narcotics is not only prohibitive in terms of cost, but also unnecessary. If the sampling procedure is respected, the Swiss Federal Supreme Court actually recognizes IMS (ion mobility spectrometry) as a lawful method for checking the degree of banknote contamination, as well as all the statistical conclusions that can be drawn from it. In special cases, the prosecutor may require confirmation of IMS results by a laboratory test (liquid/gas chromatography-mass spectrometry). Using a non-destructive sampling procedure (suction on swabs) we determined the presence of cocaine on 978 circulating euro banknotes, randomly collected at 5 swiss customs offices, with IMS and LC-MS/MS in order to establish a normal (background) contamination level. A significant proportion (46.4%) of the euro banknotes analysed by LC-MS/MS had cocaine concentrations above the quantification limit (1 ng/swab). However, the extent of contamination is a determining factor: 94.6% of the banknotes in circulation have cocaine concentrations equal to or less than 10 ng/swab and only 3.4% have cocaine concentrations above 20 ng/swab. By comparison, only 27.3% and 13.4% respectively of the seized banknotes (2 real cases) had cocaine concentrations equal to or less than 10 ng/swab, but 63.5% and 86.7% respectively had cocaine concentrations above 20 ng/swab. We also describe a Komolgorov-Smirnov test model used to determine the presence of an "abnormal" level of contamination relative to the reference banknotes (banknotes in circulation or background noise) effectively and within realistic practical and theoretical frameworks. This model provides a quantifiable and statistically significant result that not only simplifies data interpretation, but also facilitates admissibility as forensic evidence in proceedings. When applied to the sized banknotes using both IMS and LC-MS/MS data, we obtain fully consistent and sounding conclusions.

Alcohol markers in hair: an issue of interpretation

Ethyl glucuronide (EtG) and fatty acid ethyl esters (FAEEs) are metabolites of alcohol that when detected in hair can provide evidence of a person's drinking behavior. The analysis of these compounds in hair has become commonplace in recent years and has been used as evidence in legal proceedings. Despite the routine use of such toxicological analysis, the correct interpretation of alcohol biomarker hair testing can be complex, and there may be debate as to the significance of the data. This paper considers whether the accepted norm of applying interpretative cut-off values to EtG and FAEE concentrations from hair samples is appropriate, and asks whether Bayesian theory, using a likelihood ratio approach may offer greater insight as to the strength of evidence. In addition to the complexity of result interpretation in this field, the sensitivity of alcohol biomarkers in hair to distinguish low level drinking from abstinence also represents a significant challenge. The use of fingernail EtG testing as an alternative to hair analysis is explored in this paper and it is proposed that fingernails may in theory show a higher uptake of EtG than hair, and thus show potential as a useful alternative matrix to document long-term low to moderate alcohol consumption.

Interpreting γ-hydroxybutyrate concentrations for clinical and forensic purposes

INTRODUCTION

γ-Hydroxybutyric acid is an endogenous substance, a therapeutic agent, and a recreational drug of abuse. This psychoactive substance acts as a depressant of the central nervous system and is commonly encountered in clinical and forensic practice, including impaired drivers, poisoned patients, and drug-related intoxication deaths.

OBJECTIVE

The aim of this review is to assist clinical and forensic practitioners with the interpretation of γ-hydroxybutyric acid concentrations in blood, urine, and alternative biological specimens from living and deceased persons.

METHODS

The information sources used to prepare this review were PubMed, Scopus, and Web-of-Science. These databases were searched using keywords γ-hydroxybutyrate (GHB), blood, urine, alternative specimens, non-conventional biological matrices, saliva, oral fluid, sweat, hair, vitreous humor (VH), brain, cerebrospinal fluid (CSF), dried blood spots (DBS), breast milk, and various combinations thereof. The resulting 4228 references were screened to exclude duplicates, which left 1980 articles for further consideration. These publications were carefully evaluated by taking into account the main aims of the review and 143 scientific papers were considered relevant. Analytical methods: The analytical methods used to determine γ-hydroxybutyric acid in blood and other biological specimens make use of gas- or liquid-chromatography coupled to mass spectrometry. These hyphenated techniques are accurate, precise, and specific for their intended purposes and the lower limit of quantitation in blood and other specimens is 0.5 mg/L or less. Human pharmacokinetics: GHB is rapidly absorbed from the gut and distributes into the total body water compartment. Only a small fraction of the dose (1-2%) is excreted unchanged in the urine. The plasma elimination half-life of γ-hydroxybutyric acid is short, being only about 0.5-0.9 h, which requires timely sampling of blood and other biological specimens for clinical and forensic analysis. Endogenous concentrations of GHB in blood: GHB is both an endogenous metabolite and a drug of abuse, which complicates interpretation of the laboratory results of analysis. Moreover, the concentrations of GHB in blood and other specimens tend to increase after sampling, especially in autopsy cases. This requires the use of practical "cut-off" concentrations to avoid reporting false positive results. These cut-offs are different for different biological specimen types. Concentrations of GHB in clinical and forensic practice: As a recreational drug GHB is predominantly used by young males (94%) with a mean age of 27.1 years. The mean (median) and range of concentrations in blood from apprehended drivers was 90 mg/L (82 mg/L) and 8-600 mg/L, respectively. The concentration distributions in blood taken from living and deceased persons overlapped, although the mean (median) and range of concentrations were higher in intoxication deaths; 640 mg/L (280 mg/L) and 30-9200 mg/L, respectively. Analysis of GHB in alternative specimens: All biological fluids and tissue containing water are suitable for the analysis of GHB. Examples of alternative specimens discussed in this review are CSF, saliva, hair strands, breast milk, DBS, VH, and brain tissue.

CONCLUSIONS

Body fluids for the analysis of GHB must be obtained as quickly as possible after a poisoned patient is admitted to hospital or after a person is arrested for a drug-related crime to enhance chances of detecting the drug. The sampling of urine lengthens the window of detection by 3-4 h compared with blood samples, but with longer delays between last intake of GHB and obtaining specimens, hair strands, and/or nails might be the only option. In postmortem toxicology, the concentrations of drugs tend to be more stable in bladder urine, VH, and CSF compared with blood, because these sampling sites are protected from the spread of bacteria from the gut. Accordingly, the relationship between blood and urine concentrations of GHB furnishes useful information when drug intoxication deaths are investigated.

Evidence of seasonal variation of ethyl glucuronide in hair: Modeling a seven-year data series

The assessment of chronic excessive alcohol consumption by ethyl glucuronide (EtG) determination in hair is generally based on a cut-off value of 30 pg/mg recognized by regulatory authorities and scientific societies that guide the decision process. The ongoing debate about the risks connected with the straightforward application of this cut-off refers to the factors that may influence the detected EtG concentration. The present contribution to this debate evaluates the seasonal variation of the averaged EtG values along a seven-year period. Over 65 000 data points have been statistically analyzed to provide a mathematical model that interprets the data, gives insight into several influencing factors, and forecasts progressive data-points of the time series. This model shows that there is an annual pattern in the data exhibiting lower EtG concentrations during warm seasons and higher values in cold seasons. The estimated EtG cycles are characterized by the seasonal variation of ±2.78 pg/mg above and below the overall mean (with 5.56 pg/mg absolute difference overall). This seasonal factor associated with EtG quantification might result in a potential source of bias, at least in the regional/climatic conditions observed in the samples' collection area. Moreover, the EtG time series reveals that the change in the sample pre-treatment procedure has an effect on the modeled pattern as an abrupt increment (+38%) in the mean value of the EtG concentration. This change corresponds to the time when the former protocol of cutting hair into small segments before extraction was substituted by pulverization with a ball mill.