Abstract
Blood is key evidence to reconstruct crime scenes in forensic sciences. Blood identification can help to confirm a suspect, and for that reason, several chemical methods are used to reconstruct the crime scene however, these methods can affect subsequent DNA analysis. Therefore, this study presents a non-destructive method for bloodstain identification using Hyperspectral Imaging (HSI, 397–1000 nm range). The proposed method is based on the visualization of heme-components bands in the 500–700 nm spectral range. For experimental and validation purposes, a total of 225 blood (different donors) and non-blood (protein-based ketchup, rust acrylic paint, red acrylic paint, brown acrylic paint, red nail polish, rust nail polish, fake blood, and red ink) samples (HSI cubes, each cube is of size 1000 × 512 × 224, in which 1000 × 512 are the spatial dimensions and 224 spectral bands) were deposited on three substrates (white cotton fabric, white tile, and PVC wall sheet). The samples are imaged for up to three days to include aging. Savitzky Golay filtering has been used to highlight the subtle bands of all samples, particularly the aged ones. Based on the derivative spectrum, important spectral bands were selected to train five different classifiers (SVM, ANN, KNN, Random Forest, and Decision Tree). The comparative analysis reveals that the proposed method outperformed several state-of-the-art methods.
Highlights
The handling of a crime scene is an important part of successful and dynamic criminal investigations
One of the most important forms of forensic shreds of evidence found at a crime scene is body fluids
Hyperspectral Imaging (HSI) system used in this study includes an FX-10 (Specim, Spectral Imaging Ltd, Finland) Hyperspectral camera, equipped with a lens from Scheiner and a line scanner
Summary
The handling of a crime scene is an important part of successful and dynamic criminal investigations. In the case of stain detection at a crime scene, the first challenge is to develop a technique for the confirmation of a stain as a bloodstain This is because a bloodstain can be comparable to other substances in terms of color and appearance on different substrates on visual inspection [8]. This may require expertise and significant analysis [25] All these spectroscopy techniques are limited to provide the spectral information of the whole specimen instead of spatial information of the whole area under observation. Irrespective to Raman spectroscopy, Hyperspectral Imaging (HSI) with different substrates especially dark and patterned has been proposed in [26]. In this work, a bloodstain is identified against eight different blood resembling substances using the HSI system in the 397–1000 nm range. A blind experiment has been performed with a blood sample of the fourth blood donor and different blood resembling substances on each substrate for further validation of the proposed methodology
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