Hair as a source of forensic evidence in murder investigations

Use of pollen assemblages as forensic evidence in non-seasonal high-altitude soils

Forensic palynology is a tool in criminalistics that uses spores and pollen grains to link a certain geographical location with a crime scene. The comparison of the pollen assemblage of a crime-scene soil and that of footwear of suspects and victims proved to be very useful as judicial evidence in multiple environments with marked seasonality. However, its usefulness in non-seasonal high-altitude soils has not been experimentally evaluated to the same extent. For this reason, the present study addressed this information gap by undertaking a palynological study in areas with high crime rates in the city of La Paz, Bolivia. To do this, we carried out multiple experimental samplings in three locations with different types of soil and different degrees of urbanization. Specifically, we compared whether the vegetation present at the time of taking the reference samples, was reflected in the pollen rain. Results showed that the vast majority of the species present in the vegetation were found in the pollen rain, with the exception of some plant species with entomophilous pollination syndrome. We also show that the transfer between assemblages from pollen rain to footwear happened effectively, which helped identify their geographical origin, and unveiled a great number of useful indicator species.

DENSEN: a convolutional neural network for estimating chronological ages from panoramic radiographs

BACKGROUND

Age estimation from panoramic radiographs is a fundamental task in forensic sciences. Previous age assessment studies mainly focused on juvenile rather than elderly populations (> 25 years old). Most proposed studies were statistical or scoring-based, requiring wet-lab experiments and professional skills, and suffering from low reliability.

RESULT

Based on Soft Stagewise Regression Network (SSR-Net), we developed DENSEN to estimate the chronological age for both juvenile and older adults, based on their orthopantomograms (OPTs, also known as orthopantomographs, pantomograms, or panoramic radiographs). We collected 1903 clinical panoramic radiographs of individuals between 3 and 85 years old to train and validate the model. We evaluated the model by the mean absolute error (MAE) between the estimated age and ground truth. For different age groups, 3-11 (children), 12-18 (teens), 19-25 (young adults), and 25+ (adults), DENSEN produced MAEs as 0.6885, 0.7615, 1.3502, and 2.8770, respectively. Our results imply that the model works in situations where genders are unknown. Moreover, DENSEN has lower errors for the adult group (> 25 years) than other methods. The proposed model is memory compact, consuming about 1.0 MB of memory overhead.

CONCLUSIONS

We introduced a novel deep learning approach DENSEN to estimate a subject's age from a panoramic radiograph for the first time. Our approach required less laboratory work compared with existing methods. The package we developed is an open-source tool and applies to all different age groups.

Blood and sperm traces on human hair. A study on preservation and detection after 3-month outdoor exposure

Hair can retain important biological traces for forensic investigations. Forensic scientists are used to looking for such traces on clothing and skin of victims, however, when decomposition kicks in and all that remains of the victims is the skeleton, hair may be the only tissue representing the surface of the body at the time of a crime on which biological traces of an aggressor may have been left and still be detectable. Given the lack of research on this topic, this pilot study aims to assess the capacity of hair to retain semen and blood in hair, and the possibility to detect these fluids with well-known techniques and to obtain a useful genetic profile even when exposed to environmental conditions (Open Natural Environment (woods), Open Man Made Environment (urban)) for three months. Results showed that both traces were always visible and detectable with almost all techniques in the Control Environment, while in the two open environments some difficulties arose. However, biomolecular analysis was effective up to three months on both fluids in the Natural Environment and up to two months and one week respectively on blood and semen in the Man Made Environment. The Combur Test, OBTI, and Luminol were effective on blood up to three months in both environments while Sperm-HY-Liter and observation of cellular components were effective on semen up to at least 1 month and PSA testing was positive up to 1 week in both environments. The present work can be considered an encouraging starting point for the analysis of biological traces on hair in forensic contexts, regardless of the PMI, since blood and semen related to a crime may survive.

Identifying the scene of a crime through pollen analysis

The forensic analysis of pollen involves the comparison of crime scene and reference pollen samples. Successful matches are frequently used to solve time- or location-related crimes. Despite its prospects in criminal investigation, forensic palynology is still underused in casework due to inherent shortcomings such as its limited evidential weighting, scarcity of skilled palynologists dedicated to forensic casework and the laborious nature of analytical procedures. To address these challenges, the current state-of-the-art in forensic palynology is transiting from the traditional light microscopic methods that dominated the early days of palynology to more contemporary approaches like Raman spectroscopy, stable isotope analysis and DNA metabarcoding. The major challenges of these methods, however, include a lack of optimisation to forensic expectations and the unavailability of robust databases to permit accurate data interpretation, and quests to resolve these problems constitute the theme of current research. While reiterating the usefulness of pollen analysis in criminal investigation, this report recommends orthogonal testing as a way of improving the evidential weighting of forensic palynology.

Common and much less common scenarios in which botany is crucial for forensic pathologist and anthropologists: a series of eight case studies

It is commonly accepted that crime scene recovery and recording are key moments of any judicial inspection in which investigators must decide on the correct strategies to put into place. Complex outdoor scenarios, presenting partially or entirely skeletonised remains, can benefit more than others by the intervention of environmental specialists (forensic anthropologists, archaeologists, entomologists and botanists). These experts are capable of singling out, correctly recording and recovering environmental evidence that can lead to a more comprehensive reconstruction of a given criminal episode. If human remains are discovered in an outdoor scenario, the on-site presence of a botanist will guarantee a correct approach to the identification, recording and recovery of any botanical evidence. If an on-site botanist is not available, the operators must be capable of both the botanical evaluation of a scene and the implementation of correct botanical sampling protocols.

The following collection of unusual case histories that aim at underlining the efficacy of forensic botany will examine the determination of post mortem or the post depositional interval, evidence for a victim’s post mortem transfer, evidence for the identification of a primary crime scene and evidence for the identification of a victim’s dismemberment site. In another two cases, one, we will illustrate the important role that forensic botany played in the discrimination between botanical material used to voluntarily conceal a victim and vegetation that had grown naturally above a disposal site, whereas the other will highlight the protocols implemented for the identification of a murder weapon.

Optimising engagement between forensics & policing: Avoiding the dialogue of the deaf

Forensic science is increasing in the scale and scope of available or emergent capabilities to aid criminal investigations. Concurrently, investigations are increasing in complexity, with disciplines such as forensic ecology having an input into police work. The many specialisms comprising forensic ecology are helping authorities to counteract the trans-national and inter-jurisdictional criminal operations which are driven by global interconnectedness and the Internet. These factors, when combined with a rise in public oversight, and the media's unrealistic expectation that all crimes are solvable, produce a challenging environment for police investigators. This paper explores the author's experience of effective communication between police investigators and forensic practitioners and reflects on an emergent consultancy model of engagement. This option presents a change in the police operating environment, often with improved investigative outcomes.

Inventory of the Recommendations for Patients with Pollen Allergies and Evaluation of Their Scientific Relevance

Pollens are responsible for allergic rhinitis, conjunctivitis, and asthma. The incidence of these diseases, which have adversely impacted the social and professional lives of people who are allergic to pollen, has tripled in the past 25 years. Official institutes, health care institutions, public interest groups, and mainstream news media provide people who are allergic to pollen with advice aimed at reducing their symptoms. The aim of this work was to provide an inventory of the prevention guidelines in the world and to evaluate their scientific relevance. A PubMed search was carried out using specific keywords. The scientific relevance of the recommendations was evaluated based on the publications disproving or confirming their merit. The guidelines issued by 12 countries in Europe, North America, and Australia were inventoried. The recommendations for avoidance were most often based on scientific data regarding their impact on pollen exposures, but they have not been clinically validated. Several studies provided additional details, however, that allowed the guidelines to be further substantiated. These guidelines have been adopted in numerous industrialized countries in the world, and they generally appear to be of relevance.

Are your hands clean? Pollen retention on the human hand after washing

Pollen retention on clothes, footwear, hair and body has been used to link people to localities with distinctive vegetation, or soils containing distinctive palynomorphs. Little attention has been given to human skin as a possible medium for carrying a forensically important pollen load and whether this might survive attempts to remove it. We report here the results of experiments testing the retention of pollen of 10 flowering plant species on the human skin through repeated cycles of washing and drying hands, using the WHO protocol to standardize hand-washing and drying. Between 0.36% and 2.74% (mean 0.93%) of the initial pollen load was retained through a single hand-wash. Trace amounts of some species survived multiple hand-wash cycles. It is concluded that forensic analyses can be made of the pollen load of those parts of the skin that may have been in contact with palynologically distinctive vegetation, even in cases where the person involved has washed, or been washed. These observations may also be of relevance in cases where human skin became contaminated with other microscopic particulates.

The creation of an assessment tool for the analysis of two forms of heat damage in animal hair

Animal cruelty cases can involve a variety of mistreatment to domestic animals. A common source of abuse is the use of heat sources, such as ovens, hot surfaces and microwaves. Analysis of damage to skin by a veterinarian is a key aspect of these investigations but additional information can be provided by observing the hair of the animal, including heat source type and exposure time. This study developed an objective grading system for the analysis of heat damage in hairs which can be used to quantify different damage characteristics including bubbling, discolouration, expansion of hair, fractures, changes to the medulla and scales and scale removal/melting. This grading scheme was applied to the investigation of dog (Canis familiaris) skin samples with full pelage and loose hairs exposed to microwaves and a heated environment in order to identify any distinguishing damage characteristics from the two different heated environments. Samples were exposed to a furnace for 1min at different temperature ranges (50-350°C with 50°C intervals) and also a microwave at maximum power for different time periods (15, 30, 45, 60, 120, 180, 240 and 300s). Hairs were extracted for examination using high powered light microscopy and scanning electron microscopy. Overall, it can be determined that the type of damage observed is influenced by the nature of heat applied and the context and substrate in which the hair is situated at the time of exposure. Using principal component analysis (PCA) it was concluded that as temperature increases in a furnace so does the severity of each of the damage characteristics observed. It can be noted that with furnace exposure, any one of the characteristics could be used to indicate the temperature to which it has been exposed. For furnace exposed samples there was no significant difference between loose or embedded hairs. PCA analysis determined that there are two independent forms of damage that occur when hairs are exposed to microwave radiation, these are: increased bubbling and discolouration in the root and increased bubbling and discolouration of the shaft and tip. Exposure time is correlated with both the root and shaft/tip observations. The results indicated some clear distinctions between heat source and exposure useful for the objective interpretation of such evidence. This standardised approach for the observation of heat damage characteristics in animal hair provides investigators with a tool to differentiate between methods of abuse, providing a greater understanding of the crime committed.