Is it possible to detect lead derived from gunshot residues on decalcified human bone by means of a histochemical staining with sodium rhodizonate?

Colorimetric Barium Detection of Gunshot Residues on Cadaveric Human Skin: A Pilot Application for Forensic Purposes

Introduction

In this study we microscopically investigated, for the first time ever, the colorimetric detectability of barium of gunshot residues (GSR) on cadaveric human skin with gunshot wounds.

Methods

For this purpose we used two different colorimetric techniques known in the literature, namely 0.2% sodium rhodizonate (Na-R-Ba 0.2%) and sodium rhodizonate in alcoholic environment (Na-R-Ba OH 0.2%). At the same time, we have also coupled it with scanning electron microscopy with energy dispersive X-ray (SEM/EDX) analysis and the colorimetric study for the detection of lead of GSR. These techniques were applied to 16 victims who died from gunshot injuries, as well as to a control group.

Results

SEM/EDX demonstrated the presence of lead in all cases and barium in 11 of the 16 cases. The subsequent colorimetric technique with Na-R-Ba 0.2% did not show the barium of GSR in any case, unlike the Na-R-Ba OH 0.2% technique. This latter, in fact, has demonstrated the presence of this metal in 2 cases (18%). No microscopic case of false positive was recorded.

Conclusion

The evidence obtained with Na-R-Ba OH 0.2% makes this method, applied here for the first time ever, worthy of further study. Meanwhile, although this technique can certainly be applied, it cannot be separated from the contextual colorimetric investigation for lead and the use of more sophisticated techniques.

Smartphone-Based Rapid Quantitative Detection Platform with Imprinted Polymer for Pb (II) Detection in Real Samples

This paper reports the successful development and application of an efficient method for quantifying Pb2+ in aqueous samples using a smartphone-based colorimetric device with an imprinted polymer (IIP). The IIP was synthesized by modifying the previous study; using rhodizonate, 2-acrylamido-2-methylpropane sulfonic acid (AMPS), N,N'-methylenebisacrylamide (MBA), and potassium persulfate (KPS). The polymers were then characterized. An absorption study was performed to determine the optimal conditions for the smartphone-based colorimetric device processing. The device consists of a black box (10 × 10 × 10 cm), which was designed to ensure repeatability of the image acquisition. The methodology involved the use of a smartphone camera to capture images of IIP previously exposed at Pb2+ solutions with various concentrations, and color channel values were calculated (RGB, YMK HSVI). PLS multivariate regression was performed, and the optimum working range (0-10 mg L-1) was determined using seven principal components with a detection limit (LOD) of 0.215 mg L-1 and R2 = 0.998. The applicability of a colorimetric sensor in real samples showed a coefficient of variation (% RSD) of less than 9%, and inductively coupled plasma mass spectrometry (ICP-MS) was applied as the reference method. These results confirmed that the quantitation smartphone-based colorimetric sensor is a suitable analytical tool for reliable on-site Pb2+ monitoring.

Analysis of the corrosive effects of hydrochloric acid (HCl) on human bone: Preliminary microscopic study and observations for forensic purposes

The destruction of a corpse in caustic acid can cause complex forensic scenarios to deal with. Furthermore, the literature on the subject is poor, having been the few studies carried out only on animal bones. We carried out an experimental analysis on human cranial, ribs, vertebrae, and femur bone fragments. These samples were sent for dissolution by hydrochloric acid (HCl) at two different concentrations in the lab: 10% and 37%. We have performed macroscopic and microscopic histological and cytological observations at set time intervals: 3, 4, 19, 24, 48, and 72 h of immersion in acids. The purpose of the study was threefold: to investigate the temporal evolution of bone dissolution, evaluate the destructive effect of the two hydrochloric acids, and establish whether or not the human pattern of histological structure could be recognized. A more significant destructive action of HCl at 37% has been observed. In the 10% acid, the bone nature of the samples was demonstrable up to 24 h of immersion, but the human pattern of histological structure was already compromised at 19 h, being lost at 24 h. Instead, in the 37% acid, the bone nature of the sample was demonstrable only within 4 h of immersion, and the human pattern of histological structure was markedly compromised within 3 h. At 19 h of immersion, neither the recognition of the bone nor its human nature was feasible. These preliminary findings and observations may be of practical use in forensic investigations of bodies found in acidic substances, for which there is no scientific evidence to refer.

Look before washing and cleaning: A caveat to pathologists and anthropologists

Partially or totally skeletonized bodies are undoubtedly the most challenging scenario to deal with for forensic pathologists and anthropologists. Indeed, in such cases, being able to figure out the cause and manner of death is often tricky. Human remains require to be washed and cleaned before a thorough assessment of any signs of trauma. However, bones and any fragment of more or less putrefied soft tissues may be home to crucial traces for investigative purposes. They are often located in the context of apparently meaningless dirt and, sometimes they are even invisible to the naked eye. Therefore, their careless cleaning inevitably leads to an unintentional loss of such traces with a negative impact on subsequent investigations. For these reasons before proceeding with cleaning, exhaustive examination and sampling must be carried out. In particular fragments of soft tissues, even if putrefied, are absolutely not to be considered as a hindrance for forensic purposes, since they could still provide valuable information after histological examination. Finally, forward-thinking professionals should think about the possible presence of exogenous micro-traces of forensic concern and collect specimens to be analyzed through in-depth analyses, such as Scanning Electron Microscopy with Energy Dispersive X-ray Spectrometry (SEM/EDX). The present series of cases demonstrates that crucial forensic information can be obtained through the analysis of apparently meaningless residues and even of micro-traces not visible to the naked eye and mixed with trivial dirt.