Near-infrared spectroscopy combined with chemometrics to classify cosmetic foundations from a crime scene

Cosmetic smears are a form of trace evidence that can link the crime scene, suspects, and victims. Foundation and lipstick are the most common sources of cosmetics that can easily smear, with most current research focused on the evidential analysis of lipsticks. This research aims to create a database of cosmetic foundations on different materials and to access the robustness of using Near-infrared with chemometrics as a non-destructive technique to identify unknown samples collected from a crime scene. Small amounts of six shades of three brands of foundations were smeared on clothing materials, which were then analysed with a combination of Near-infrared with chemometric analysis. Principle component analysis (PCA) was used to reduce data dimensionality and explore potential patterns in sample separation and Linear Discriminant Analysis (LDA) was utilised to assign unknown samples to one of the established classes. The selected techniques proved to be promising for database construction and as a preliminary method of analysis, with 93% of the spectra being correctly classified. Notably, darker foundation shades were less likely to be correctly classified (90% classified correctly) compared to lighter ones (96.7% classified correctly). This could not be improved with Standard Normal Variate (SNV) data pre-treatment or selecting specific NIR regions. This finding is of particular importance; according to the Crime Survey for England and Wales (year ending March 2020) police recorded sexual offences demonstrated that those in Mixed and Black or Black British ethnic groups were significantly more likely to be a victim of sexual assault compared to White, Asian or Other ethnic groups. It is, therefore, crucial to add a wide range of foundation shades, particularly of darker tones, to the future database.

Determination of ethanol in micro-volumes of blood by headspace gas chromatography: Statistical comparison between capillary and venous sampling sites

Ethanol is the most commonly encountered drug in forensic toxicology, with widespread use throughout society. For this reason, it is important that there are a variety of reliable and robust methods to detect and quantify the content of alcohol in blood samples of suspected drink drivers. A common method of detection is gas chromatography with flame ionisation detector, with a number of sample preparation techniques employed. Typically, venous blood is sampled and used in the analysis. However, there is currently no legal specification in the UK of the blood sample source. This study investigates the use of capillary blood as an alternative to venous blood alongside two different sample volumes: 100 and 10 µL. Venous and capillary blood were collected from volunteers who had consumed alcohol. All blood sampling was carried out one hour after cessation of drinking. The results show a statistically significant difference between venous and capillary samples, with an average difference of 3.38 ± 1.99 mg/100 mL at 100 μL and approximately 4.13 ± 2.42 mg/100 mL at 10 μL, respectively. Predominantly, venous blood was detected at higher concentrations than the corresponding capillary samples. The deviations in alcohol samples between venous and capillary blood are consistent with previous studies. However, our research indicates that capillary blood is a viable matrix to test for alcohol, albeit one that underestimates blood-alcohol content in relation to venous sampling. There was no statistically significant difference between the 100 and 10 µL sample preparation methods on an individual basis, which infers that micro-volumes of alcohol are suitable for forensic blood-alcohol analysis.

Toxicological Assessment of the Role of Alcohol and Drugs in Drug-Facilitated Sexual Assault Cases in New Zealand

This report details the toxicology profile of victims of drug-facilitated sexual assault (DFSA) in New Zealand from 2015 to 2018. This study represents all of the toxicology results for DFSA cases in New Zealand during this time period, of which there were 161 cases. Blood and urine samples were screened for legal and illicit drugs in addition to testing for alcohol and correlating alcohol concentration with sampling delay. Our results indicate that increased delay in sampling time resulted in a corresponding decrease in alcohol concentration. In victims who had declared alcohol use but of which none was detected, the average sampling time was 14 hours for blood and 17 hours for urine, which is in excess of the average sampling delay for even the lowest alcohol-positive samples. The most frequently detected alcohol concentration was in the range of 51-80 mg/100 mL for blood and 121-200 mg/100 mL for urine with an average sampling time of 8.5 and 6.5 hours, respectively. We also examined acetone concentrations in alcohol-positive samples, and our results indicate that 82% of blood alcohol-positive samples contained acetone at concentrations between 5 and 10 mg/L and 68% of alcohol-positive urine samples contained acetone at a concentration >20 mg/L. It may be that the nature of sexual assault affects an individual's metabolism of alcohol and results in increased acetone production. Cannabis was the most commonly detected illicit drug, followed by methamphetamine. In relation to medicinal drugs, there was a high usage of antidepressants and antipsychotics, suggesting the victims may have been people of vulnerable personality. Based on case information, it does not appear there are many cases where stupefaction by unknown administration of a drug has occurred, instead loss of consent through voluntary alcohol and drug consumption is more common and poses a greater risk than surreptitious drug administration.