The non-contact detection and identification of blood stained fingerprints using visible wavelength reflectance hyperspectral imaging: Part 1

Abstract

Blood is one of the most commonly encountered types of biological evidence found at scenes of violent crime and one of the most commonly observed fingerprint contaminants. Current visualisation methods rely on presumptive tests or chemical enhancement methods. Although these can successfully visualise ridge detail, they are destructive, do not confirm the presence of blood and can have a negative impact on DNA sampling. A novel application of visible wavelength reflectance hyperspectral imaging (HSI) has been used for the detection and positive identification of blood stained fingerprints in a non-contact and non-destructive manner on white ceramic tiles. The identification of blood was based on the unique visible absorption spectrum of haemoglobin between 400 and 500 nm. HSI has been used to successfully visualise ridge detail in blood stained fingerprints to the ninth depletion. Ridge detail was still detectable with diluted blood to 20-fold dilutions. Latent blood stains were detectable to 15,000-fold dilutions. Ridge detail was detectable for fingerprints up to 6 months old. HSI was also able to conclusively distinguish blood stained fingerprints from fingerprints in six paints and eleven other red/brown media with zero false positives.

The non-contact detection and identification of blood stained fingerprints using visible wavelength hyperspectral imaging: Part II effectiveness on a range of substrates

“…One of the key issues involving optical analysis of fingerprints is to ensure sufficient ridge detail is captured to allow for comparison of crime scene marks against fingerprints from a suspect. The first part of this study [9] investigated the novel use of hyperspectral imaging for the analysis of blood stained fingerprints on white tiles. The main focus was to establish if ridge detail of a sufficient resolution could be determined, to potentially allow for fingerprint comparison.…”

A comparison of visible wavelength reflectance hyperspectral imaging and Acid Black 1 for the detection and identification of blood stained fingerprints

“…The approach carried out by our research group indicated a higher sensitivity and specificity for the detection and identification of blood stains over previously proposed methods [3]. Recent research has since successfully demonstrated the application of this technique for the detection, identification, and visualisation of ridge detail in blood stained fingerprints deposited on white ceramic tiles [19] and a range of other substrates commonly encountered at scenes of crime [20]. To date there has been no comparison between HSI and existing chemical enhancement methods, such as Acid Black.…”

“…The HSI system used in this study was the same setup detailed in [3] and [19,20], consisting of a liquid crystal tuneable filter (LCTF) coupled to a 2.3 megapixel Point Grey camera and a light source for scene illumination. The light source was comprised of two 40W LEDs; one violet giving an output at 410nm and one white giving an output between 450 and 700 nm.…”

“…The hyperspectral reflectance measurements were made following the method detailed in [3] and [19,20]. A reference image (R 0 ) was obtained using a blank ceramic tile.…”

“…Results potentially indicate a significant step towards a reliable method for both non-destructive blood identification and the detection of ridge detail in blood stained fingerprints, both before and after chemical enhancement. This work is following on from [19,20], where hyperspectral imaging was demonstrated for the first time to detect, identify, and visualise to a sufficient resolution the ridge detail of blood stained fingerprints across a wide range of substrates. The research presented in this paper again demonstrates the potential of HSI, through a comparison of the successful nondestructive detection and identification of blood stained fingerprints against Acid Black chemical enhancement.…”