Abstract

In this paper we demonstrate that micronised Egyptian blue pigment can be used as a safe and simple material to visualise latent fingerprints on non-porous surfaces as near-infrared luminescent impressions. This allows the detection of latent fingerprints on highly patterned and reflective surfaces that have proven challenging with existing techniques.

Introduction

The detection of latent fingerprints is extremely useful in forensic investigations to establish evidence of contact between the criminal, the victim, and/or the crime scene [1-3]. To that end, a wide range of chemical and physical methods have been developed to aid in their detection and recovery, the choice of which is dependent on the nature of the surface involved [1,2]. The most common approach to detecting latent fingerprints on non-porous items has been the use of dusting powders, which work through physical adhesion to the latent fingerprint deposit [1-5]. It has been estimated that in the United Kingdom, approximately 50% of the 60,000 fingerprint identifications per annum arise from powdered fingerprints [1]. Historically, a wide range of materials have been utilised as fingerprint powders; including carbon black, iron oxide-based magnetic powder and titanium dioxide; in attempts to achieve improved visualisation across a wide variety of surfaces and conditions [1-5]. In recent times, this has included attempts to use natural products such as turmeric as safe and inexpensive powders [6]. Several commercially available powders exhibit luminescence in the visible region of the electromagnetic spectrum, which to some extent can negate the interferences exhibited by highly patterned or coloured surfaces [1,2,4]. However, there remain many fluorescent, highly patterned and/or reflective surfaces that continue to prove troublesome [7-9].