Une méthode permettant de dater un tir est présentée. La technique analytique est décomposée en deux étapes: d'abord un prélèvement par microextraction en phase solide (SPME) à l'intérieur du canon d'un fusil de chasse, suivi d'une analyse par chromatographie en phase gazeuse couplée à un détecteur à ionisation de flamme (GC/FID) ou à un spectromètre de masse (GC/MS). Des produits typiques résultant d'une combustion incomplète ont été détectés et dix d'entre eux ont été identifiés comme étant des hydrocarbures polycycliques aromatiques (HPA). L'analyse simultanée de quatre de ces HPA (naphtalène, 1-méthyl naphtalène, 2-méthyl naphtalène et acénaphtylène) confirme que le fusil de chasse suspecté a tiré récemment, quel que soit le couple munition-arme. L'évaluation de la date du tir est basée sur le taux d'échappement de ces HPA hors du canon du fusil. Une mesure quotidienne de l'aire du pic de naphtalène peut permettre une évaluation de la date d'un tir sous certaines conditions. Tout d'abord, l'origine des HPA sera examinée en étudiant différentes munitions. Puis, la technique analytique sera expliquée avant l'étude de différents paramètres, telles les conditions environnementales lors du tir, la longueur des canons et leur obturation, la présence de lubrifiant et enfin, le nombre de tir. ABSTRACT A procedure to estimate the time since the last gunshot is presented. The analytical technique consists of Solid Phase Micro-Extraction (SPME) sampling inside the shotgun barrel, followed by analysis using gas chromatography coupled with flame ionisation detection (GC/FID) or mass spectrometry (GC/MS). Typical products resulting from an incomplete combustion were detected and ten of them were identified as Polycyclic Aromatic Hydrocarbons (PAH). Simultaneous analysis for four of these PAH (naphthalene, 1-methylnaphthalene, 2-methylnaphthalene, and acenaphtylene) confirmed that the suspected firearm had been fired recently, regardless of the ammunition and firearm used. The time estimation was based on the rate of escape of these PAH from the firearm barrel. Daily monitoring of the naphthalene peak area can give an estimate of the time since the last gunshot, based on conditions after firing. First, PAH origins are examined by studying different ammunitions. Then, the developed analytical technique is explained before studying different key parameters, such as immediate environmental conditions after shooting, barrel sealing, barrel length, lubricant influence, and number of gunshots.
The Forensic Science Institute of the French "Gendarmerie Nationale" (IRCGN™) developed in 2015 an ISO 17025 certified mobile DNA laboratory for genetic analyses. This Mobil'DNA laboratory is a fully autonomous and adaptable mobile laboratory to perform genetic analyses in the context of crime scenes, terrorism attacks or disasters. To support the hospital task force in Paris during the peak of the COVID-19 epidemic, we adapted this mobile genetic laboratory to perform high-throughput molecular screening for coronavirus SARS-CoV-2 by real-time PCR. We describe the adaptation of this Mobil'DNA lab to assist in Coronavirus SARS-CoV-2 diagnosis.
The emergence and quick spread of SARS-CoV-2 has pointed at a low capacity response for testing large populations in many countries, in line of material, technical and staff limitations. The traditional RT-qPCR diagnostic test remains the reference method and is by far the most widely used test. These assays are limited to a few probe sets, require large sample PCR reaction volumes, along with an expensive and time-consuming RNA extraction step. Here we describe a quantitative nanofluidic assay that overcomes some of these shortcomings, based on the BiomarkTM instrument from Fluidigm. This system offers the possibility of performing 4608 qPCR end-points in a single run, equivalent to 192 clinical samples combined with 12 pairs of primers/probe sets in duplicate, thus allowing the monitoring of SARS-CoV-2 including the detection of specific SARS-CoV-2 variants, as well as the detection other pathogens and/or host cellular responses (virus receptors, response markers, microRNAs). The 10 nL-range volume of BiomarkTM reactions is compatible with sensitive and reproducible reactions that can be easily and cost-effectively adapted to various RT-qPCR configurations and sets of primers/probe. Finally, we also evaluated the use of inactivating lysis buffers composed of various detergents in the presence or absence of proteinase K to assess the compatibility of these buffers with a direct reverse transcription enzymatic step and we propose several protocols, bypassing the need for RNA purification. We advocate that the combined utilization of an optimized processing buffer and a high-throughput real-time PCR device would contribute to improve the turn-around-time to deliver the test results to patients and increase the SARS-CoV-2 testing capacities.
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