Investigation of infinite focus microscopy for the determination of the association of blood with fingermarks

Abstract

The determination of the type of deposition mechanism of blood within fingermarks at the scene of violent crimes is of great importance for the reconstruction of the bloodshed dynamics. However, to date, evaluation still relies on the subjective visual examination of experts. Practitioners encounter three types of scenarios in which blood may be found in fingermarks and they refer to the following three deposition mechanisms: (i) blood marks, originating from a bloodied fingertip; (ii) marks in blood, originating from a clean fingertip contacting a blood contaminated surface; (iii) coincidental deposition mechanisms, originating from a clean fingertip contacting a clean surface, leaving a latent fingermark, and subsequent contamination with blood.. The authors hypothesised that, due to differences in distribution of blood in the furrows and on the ridges, the height of blood depositions on the ridges and furrows (and their relative proportions), will differ significantly across the three depositions mechanisms. A second hypothesis was made that the differences would be significant and consistent enough to exploit their measurement as a quantitative and objective way to differentiate the deposition mechanisms. In recent years, infinite focus microscopy (IFM) has been developed, allowing for the computational generation of a 3D image of the topology of a sample via acquisition of images on multiple focal planes. On these bases, it was finally hypothesised that the application of this technique would allow the distinction of deposition mechanisms (i) to (iii) A set of preliminary experiments were designed to test whether IFM was "fit for purpose" and, subsequently, to test if any of the three deposition mechanisms scenarios could be differentiated. Though IFM enabled the analysis of tape lifted samples with some success, for samples produced and analysed directly on the surface of deposition, the results show that the measurements from any scenario will be highly dependent on the original surface of deposition (both in terms of its nature and of the variable exposure to environment); as crime scenes exhibit a wide range of possible relevant surfaces of deposition, the technique showed to not have the desired wide appeal for inclusion into a standardised set of protocols within a routine crime scene workflow.

Imaging mass spectrometry: a new way to distinguish dermal contact from administration of cocaine, using a single fingerprint

“…[6][7][8][9][10][11][12] There is also growing evidence to support the concept of using a fingerprint to provide information concerning the circumstances of depositionso-called "activity level information". [13][14][15] Meanwhile, in its latest World Drug Report 2020, the United Nations Office on Drug and Crime (UNODC) reports that as of 2018 approximately 5.3% (or 269 million people) of the global population aged 15-64 had used illicit drugs in the previous year. There are an estimated 19 million cocaine users globally, and an all-time high production of cocaine.…”

Detection and mapping of haemoglobin variants in blood fingermarks by MALDI MS for suspect “profiling”

“…Over the past seven years, Matrix Assisted Laser Desorption Ionisation has proven its capability to detect and visualise blood in stains and fingermarks. [1][2][3][4][5][6] The compatibility with a range of blood enhancement techniques as well as its feasibility of application in aged blood (as old as 37 years 5 ) confer the technique operational significance. Recently, it has been possible to provide additional information from this evidence by establishing its human or animal provenance (down to animal species) as well as discriminating this from other biological matrices 4,[6][7][8][9] and in a pre-validation study.…”

Application of 3D Imaging Technology to Latent Fingermark Aging Studies

“…In recent years, there has been a significant improvement in optical contactless 3D technology (i.e., microscopes) leading to increased quality in the acquisition of images and quantitative measurements . The work has been mostly focused on the acquisition and preprocessing of fingermarks in 3D or for the analysis of their chemical components but has not been generally applied to aging studies . Of the array of technologies, optical profilometers (OPs) are used to measure surface roughness of materials.…”