Explosion Scene Forensic Image Interpretation.

Image interpretation is an important aspect in the field of forensic science; however, it is seldom reported how to use these techniques in explosion scene forensic investigations. On 12 August 2015, a series of explosions killed 165 people and injured hundreds more at a container storage station at the Port of Tianjin. In this study, we applied image interpretation methods to determine the seat of the explosion by analyzing low-quality video clips of the event. The interpretation fits well with recently published standard operating procedures, including the hypothesis, evaluation, inference, and confirmation. Image processing was adopted to enhance the images while the explosion scene was reconstructed with the same images. Some important features were extracted and utilized to distinguish whether the flashes were caused by reflection or a real blast. We reveal the real explosion location, which guides the overall investigation. The results indicate that image interpretation is a powerful tool for forensic investigators to analyze low-quality images in complicated explosions or fire accidents.

Capillary electrophoretic fingerprint investigation of gel pen inks.

In this study, two capillary electrophoresis modes, capillary zone electrophoresis (CZE) and micellar electrokinetic chromatography (MEKC), were employed for the examination of gel ink fingerprints. The optimized CZE conditions were as follows: running buffer, 0.2M boric acid and 0.05M sodium tetraborate; pH, 6.47; detection, 214 nm; separation voltage, 20 kV MEKC conditions were as follows: 20 mM sodium tetraborate-20 mM sodium dodecyl sulphate; detection, 214 nm; separation voltage, 20 kV. The CZE and MEKC fingerprints of 18 el pen inks from Beijing markets were analyzed and the inks were classified according to the fingerprints of the two CE modes.

Elemental analysis of white electrical tapes by wavelength dispersive X-ray fluorescence spectrometry.

The aim of this study was to analyze and discriminate electrical tapes using the wavelength dispersive X-ray fluorescence (XRF) spectrometry and statistical techniques. The backings of 46 white electrical tapes were analyzed. A discrimination of 90.4% was performed only by quantitative analysis of major elements (relative ratio of Cl to Ca). Ten distinct groups with a discrimination of 78.9% were yielded only by qualitative analysis of trace elements. Ninety-nine electrical tape pairs which could not be discriminated by major elements were further compared with the characteristics of trace elements. The overall discriminating power of 96.1% was obtained by the combination of quantitative and qualitative analysis. The ability of XRF technique to discriminate different electrical tapes was similar to several well-known methods combined.

[Determination of inorganic ions in explosive residues by capillary zone electrophoresis].

Five anions (chlorate, perchlorate, nitrate, nitrite, and sulfate) and two cations (ammonium and potassium) in explosive residues have been separated and determined by capillary zone electrophoresis (CZE) with indirect ultraviolet detection. The electrolyte buffer for the cation separation was 10 mmol/L pyridine (pH 4.5) -3 mmol/L 18-crown-6-ether. Ammonium and potassium ions were baseline separated in less than 2.6 min with the detection limits of 0.10 mg/L and 0.25 mg/L (S/N = 3), respectively. The electrolyte buffer for the anion separation consisted of 40 mmol/L boric acid-1.8 mmol/L potassium dichromate-2 mmol/L sodium tetraborate (pH 8.6), and tetramethyl ammonium hydroxide (TMAOH) was used as electroosmotic flow modifier. All five anions were well separated in less than 4.6 min with the detection limit range of 0.10 - 1.85 mg/L (S/N = 3). The method was successfully used in real sample investigations to confirm the type of explosives.