Tattoos and human identification: investigation into the use of X-ray and infrared radiation in the visualization of tattoos

On the forensic relevance of tattoos: distinguishing black inks with energy dispersive spectroscopy and backscattered scanning electron microscopy

PURPOSE

This study aimed to analyze black tattoo inks by means of energy dispersive spectroscopy and backscattered scanning electron microscopy.

METHODS

The sample consisted of five types of commercial tattoo pigments of the black colour (Easy Glow™, Electric Ink™, Iron Works™, Master Ink™, and Viper™). An Energy Dispersive Spectroscopy (EDS) detector (Silicon Drift Detector - SDD - type) attached to a Scanning Electron Microscope (SEM) device (Tescan Vega3 LMU, Libusina, Czech Republic) was used. X-ray characteristic signs were detected for each tattoo ink in an interval between 0 and 2.5 keV. The electron acceleration potential in the microscope was 15 keV. Two regions were analyzed for each sample (n = 10). On each region, a micrography of backscattered electrons (BSE) was obtained. Means and standard deviations (SD) of the weight percentages (Wt%) were calculated.

RESULTS

C and O were predominant, with a mean O/C ratio between 2.69 and 2.74 Wt%. Electric Ink and Master Ink were the most similar pigments, while Easy Glow was the most distinctive - with agglomerates of Al that had a concentration 25 × higher than other specimens. Other compounds detected in the sample were Cl and Cu.

CONCLUSION

EDS and SEM were efficient to distinguish black tattoo inks. These are our preliminary outcomes on the use of EDS and SEM to analyze black tattoo inks. Thus, careful interpretation is necessary to avoid rash applications in human identification practice.

Optimization and standardization of procedures in Forensic Identification: A methodology for description and coding of tattoos in Mexico

Tattoos serve as a valuable tool for identification. In the forensic context, it is vital to establish a systematic approach for documenting tattoo-related information to facilitate efficient and fast comparisons, especially in postmortem cases. Despite some countries failing to recognize the potential significance of tattoos, this study presents a methodological framework for gathering comprehensive data on this form of body modification. This article presents the results of an investigation made in Mexico during 2019-2022. The proposed methodology introduces a systematic and distinct classification system tailored to the country in which it will be implemented. The proposal is accompanied by applying the methodology in a Forensic Medical Service (SEMEFO) in Mexico for a week to test its effectiveness and speed under high workloads and stressful conditions. The novelty of this article lies in emphasizing the need for established, replicable, and homologous methodologies for tattoo codification. Additionally, it presents a more in-depth codification, where the details of the tattoos to be classified are thoroughly analyzed.

Beyond the visible spectrum - applying 3D multispectral full-body imaging to the VirtoScan system

Multispectral photography offers a wide range of applications for forensic investigations. It is commonly used to detect latent evidence and to enhance the visibility of findings. Additionally, three-dimensional (3D) full-body documentation has become much easier and more affordable in recent years. However, the benefits of performing 3D imaging beyond the visible (VIS) spectrum are not well known, and the technique has not been widely used in forensic medical investigations. A multicamera setup was used to employ multispectral photogrammetry between 365 and 960 nm in postmortem investigations. The multicamera setup included four modified digital cameras, ultraviolet (UV) and near-infrared (NIR) light sources and supplemental lens filters. Full-body documentation was performed in conjunction with the use of a medical X-ray computed tomography (CT) scanner to automate the imaging procedure. Textured 3D models based on multispectral datasets from four example cases were reconstructed successfully. The level of detail and overall quality of the 3D reconstructions varied depending on the spectral range of the image data. Generally, the NIR datasets showed enhanced visibility of vein patterns and specific injuries, whereas the UV-induced datasets highlighted foreign substances on the skin. Three-dimensional multispectral full-body imaging enables the detection of latent evidence that is invisible to the naked eye and allows visualization, documentation and analysis of evidence beyond the VIS spectrum.

Human identification: a review of methods employed within an Australian coronial death investigation system

Whilst many identification methods have been widely described and discussed in the literature, and considered in disaster and humanitarian contexts, there has been limited reporting and evaluation of the identification methods used in domestic medico-legal death investigation contexts. The aim of this study was to evaluate the identification methods utilised at the Victorian Institute of Forensic Medicine (VIFM), which forms part of a coronial medico-legal death investigation system. The method of identification and time taken to complete the identification were reviewed for all cases admitted to the VIFM over a five-year period from 1 July 2015 to 30 June 2020. The majority, 91%, of individuals admitted to the VIFM were visually identified. The remaining 9% of cases required identification by primary methods (i.e. fingerprints, DNA or dental) or, when those methods were not possible, by secondary methods (i.e. circumstantial). Visual identifications were the timeliest, taking an average of 1.5 days, whilst primary identification methods required an average of 5 days to complete. The triaging of identification methods, dependent on the case context, body preservation, availability of ante-mortem data, legal requirements and admissibility of the method, are determined by identification coordinators within the Human Identification Service (HIS) to ensure the most appropriate and timely method is employed. This review of human identification methods provides the foundation for future analyses to compare workflow processes and improve identification methods utilised in domestic medico-legal contexts.

Tattoo in forensic science: An Indian perspective

BACKGROUND

- Tattoos refer to various skin markings done by impregnating the skin's epidermis with varied pigments. In forensic science, tattoos are considered as secondary identification markers and can be used for positive identification. Indian society is a unique blend of traditional and modern religious and social practices. Thus, traditional tattoos are still prevalent among various tribal societies and scheduled castes spread throughout various parts of India. The tribal tattoos can be used to determine tribal affiliations, that can aid in the process of forensic identification. On the other hand, tattoos comprising Western-influenced designs as well as individuals co-opting traditional designs gradually are becoming more popular in urbanized India. Understanding and documenting the various tattoo patterns prevalent throughout the tribal population and the modern metropolitan cities can help create a reference base line data for future forensic identification.

Beneath cover-up tattoos: possibilities and limitations of various photographic techniques

BACKGROUND

The goal of this study was to investigate the usefulness of various photographic techniques in visualizing previous tattoos under cover-up tattoos.

MATERIAL AND METHODS

Ten volunteers with 11 known cover-up tattoos were examined using different photographic techniques: A Canon EOS 6D full-frame digital single-lens reflex camera used in conjunction with a SB600 off-camera flash system and an extension cord; and a Leica M8 digital imaging system camera in conjunction with two different infrared filters (715 nm and 850 nm) and a Metz CL-45 handle-mount flash. A Lumatec Superlite 400 forensic light source was used along with the Canon EOS 6D as a third system.

RESULTS

The best results for black cover-up tattoos were achieved with the full-frame digital single-lens reflex camera in conjunction with the off-camera flash system and, for colored cover-up tattoos, with IR-photography at a wavelength of 850 nm. The Lumatec Superlite 400 light source did not provide better results for conventional photography than those obtained with flash lighting.

DISCUSSION

In nine out of eleven cover-up tattoos, the previous tattoos could, at least, be partially visualized. The quality of the visualization depended on the color, pattern, density, and quality of the cover-up tattoo as well as on the photographic technique. None of the examined photographic techniques could satisfactorily image the previous tattoo if the cover-up tattoo was large and black, especially not if it was densely inked.

CONCLUSION

Depending on the color of the cover-up tattoo, a full-frame digital single-lens reflex camera in conjunction with a SB600 off-camera flash system (for black cover-ups) or infrared photography with flash lighting and an 850 nm filter (for colored cover-ups) proved to be the best of the investigated techniques to visualize a previous tattoo under a cover-up tattoo.

Tattoo image composed of radiopaque deposits demonstrated by postmortem computed tomography

Postmortem computed tomography (PMCT) is becoming used more commonly in routine forensic investigation. CT is sensitive for detection of metal foreign bodies. Here we report a case of suicide due to self-ignition of kerosene that the victim had poured over herself. Prior to autopsy, PMCT detected tiny radiopaque particles arranged in a row in the surface of the back and either thigh, together with a series of similar particles under the skin lateral to the breasts or the bilateral inguinal region. At autopsy, external examination revealed third-degree burns involving charred tissues all over the body except for the head. Tattoos were visible on the back and on either thigh. The tattoos had colored designs, and the red portions corresponded to the radiopaque particles in the surface of the body. Internal examination demonstrated swelling of the axillary and inguinal lymph nodes, which corresponded to the radiopaque particles. A wave length-dispersive X-ray spectroscopy revealed deposition of mercury and titanium in the inguinal lymph nodes. Thus, it was plausible that the ink could have contributed to the radiopaque particles found by PMCT in the surface of the back and thighs, as well in the lymph nodes. The present case was able to provide clues for interpretation of radiopaque particles revealed by PMCT in the surface of the body.

Relatively Permanent Pigmented or Vascular Skin Marks for Identification: A Pilot Reliability Study

In child sexual exploitation offenses, the collected evidence images often show the skin of nonfacial body parts of the criminals and victims. For identification in this scenario, "relatively permanent pigmented or vascular skin marks," abbreviated as RPPVSM, were recently introduced as the basis for a novel biometric trait. This pilot study evaluated the interexaminer variability of RPPVSM identification. Four dermatology physicians were recruited to examine RPPVSM from 75 skin images collected from a total of 51 Caucasian and Asian subjects. The images were separated into 50 reference ("suspect") images and 25 evaluation ("evidence") images. The examiners were asked to perform identification by annotating RPPVSM in each of the 25 evaluation images and matching them with the reference images. The rate of misidentification was 0% while the mean rate at which examiners failed to find a match was 6%, indicating the potential of dermatology physicians performing the role of RPPVSM examiners.