RESUMO

This retrospective study reports data obtained by the Federal Police's National Institute of Criminalistics (INC-PF) relating to chemical analysis aimed at identifying explosives used in Automated teller machines (ATMs)/cash safes robberies between 2014 and 2020 in Brazil. 93 Real cases were studied and, based on the analysis carried out on the materials related to these cases, focusing on the type of explosive used, the following distribution profile was obtained: I) explosive mixtures based on chlorates and/or perchlorates (53%); explosive emulsion (22%); black gunpowder (13%); negative/inconclusive (11%) and organic - pentaerythritol tetranitrate (PETN) (1%). These results can contribute to investigations related to diversion/loss of explosives for criminal purposes, indicating, for example, through relationships between prevalence in the use of a certain type of explosive with a certain location, its possible origin (mining industry, explosive industries, fireworks factories, among others). The profile observed in the results can guide the selection of explosives to be studied in future research, as the possibilities are vast. Furthermore, despite the expressive number of occurrences in Brazil in the period of interest of this study, only a small fraction of samples was sent to the forensic chemistry laboratory to identify the explosive involved, which suggests that expanding chemical analysis should be encouraged in this field. In combination with an increase in professional training and collaboration trials between the laboratories, these activities can improve the chemical explosive's profile in Brazil, enabling the search for correlations between occurrences and contributing to the growth and development of this area.

Assuntos

RESUMO

Analysis of explosive residues is of special interest in forensic science. It can be crucial for investigating acts of terrorism or robberies. Ion Chromatography (IC) is a standard technique used by many forensic labs in these cases. Due to the common nature of many explosives and the inherent dirtiness of samples from explosion scenes, sometimes inconclusive or false positive results are obtained by IC, making the identification of interferers extremely important. One possible source of interferer can be the sampling materials themselves, as investigated in this work. First of all, interferers from forensic swabs and syringe filters were evaluated, as these are commonly employed in explosive residue IC analysis. Among the 6 tested samples, only two syringe filters were considered free of interferers. Significant amounts (>0.2mg/L) of Na+, K+, Mg2+, Ca2+, Cl-, and SO42- were found in all forensic swabs and two syringe filters. Then, some ordinary commercial materials, such as cotton swabs, cotton balls, and cotton discs were also tested, as they are often employed in a forensic routine, also. These also showed significant amounts (>0.2mg/L) of Na+, K+, Cl-, NO3-, and SO42-. However, the total concentration of interferers in ordinary commercial materials was lower than in the forensic swabs. Then the effectiveness of removing interferers by washing sampling (swabs, and cotton balls, rolls and disk) and pre-processing (syringe filters) materials was evaluated. This revealed that the interferers could be removed with at least three washes. The results indicated that the sampling materials used for explosion scene analysis should be carefully addressed in forensic analysis. First, by making a previous analysis of the sampling material, preferably prior to use, to evaluate the presence of interferers to ensure that only material free of interferers is used. When it is not possible to perform a prior analysis of sampling materials, they should be analyzed concomitantly with the samples from the post-blast residue in order to estimate the presence of interferers. This would reduce the risk of false positives. Additionally, when interferers are detected, washing can be employed for more reliable routine analysis. We suggest at least 3 wash cycles. This method could be used for ordinary commercial materials, which are cheap and easily obtained.

RESUMO

In this work, Raman hyperspectral imaging, in conjunction with independent component analysis, was employed as an analytical methodology to detect an ammonium nitrate fuel oil (ANFO) explosive in banknotes after an ATM explosion experiment. The proposed methodology allows for the identification of the ANFO explosive without sample preparation or destroying the sample, at quantities as small as 70µgcm-2. The explosive was identified following ICA data decomposition by the characteristic nitrate band at 1044cm-1. The use of Raman hyperspectral imaging and independent component analysis shows great potential for identifying forensic samples by providing chemical and spatial information.

RESUMO

This report describes for the first time the use of microchip electrophoresis (ME) devices integrated with capacitively coupled contactless conductivity detection (C4 D) to investigate the authenticity of seized whiskey samples, which were probably adulterated by simple dilution with tap water. The proposed microfluidic platform was explored for the monitoring of anionic species (Cl- and F- ) in both original and tampered samples. The best separations were achieved within 70 s using a running buffer composed of lactic acid and histidine (pH = 5.9). ME-C4 D devices were used to analyze samples from three different brands (five samples each). Based on the presence of inorganic anions like Cl- , F- , SO42- and NO2- in different amounts, the authenticity of seized whiskeys was compared to original samples. According to the reported data, the proposed microfluidic platform can be useful to help regulatory authorities in the investigation and monitoring of authenticity of commercialized whiskey beverages.

Assuntos

RESUMO

The aim of this study was to develop a methodology using Raman hyperspectral imaging and chemometric methods for identification of pre- and post-blast explosive residues on banknote surfaces. The explosives studied were of military, commercial and propellant uses. After the acquisition of the hyperspectral imaging, independent component analysis (ICA) was applied to extract the pure spectra and the distribution of the corresponding image constituents. The performance of the methodology was evaluated by the explained variance and the lack of fit of the models, by comparing the ICA recovered spectra with the reference spectra using correlation coefficients and by the presence of rotational ambiguity in the ICA solutions. The methodology was applied to forensic samples to solve an automated teller machine explosion case. Independent component analysis proved to be a suitable method of resolving curves, achieving equivalent performance with the multivariate curve resolution with alternating least squares (MCR-ALS) method. At low concentrations, MCR-ALS presents some limitations, as it did not provide the correct solution. The detection limit of the methodology presented in this study was 50 µg cm(-2).

RESUMO

Ammonium nitrate fuel oil (ANFO) is an explosive used in many civil applications. In Brazil, ANFO has unfortunately also been used in criminal attacks, mainly in automated teller machine (ATM) explosions. In this paper, we describe a detailed characterization of the ANFO composition and its two main constituents (diesel and a nitrate explosive) using high resolution and accuracy mass spectrometry performed on an FT-ICR-mass spectrometer with electrospray ionization (ESI(±)-FTMS) in both the positive and negative ion modes. Via ESI(-)-MS, an ion marker for ANFO was characterized. Using a direct and simple ambient desorption/ionization technique, i.e., easy ambient sonic-spray ionization mass spectrometry (EASI-MS), in a simpler, lower accuracy but robust single quadrupole mass spectrometer, the ANFO ion marker was directly detected from the surface of banknotes collected from ATM explosion theft.