INTRODUCTION
At a crime scene, most of the information (evidence) can be used to provide information for
evaluating what did or could not have happened and involving whom.
Fingerprints are a type of evidence that are often found at crime. Unique characteristics, and the unchanged friction ridge of each individual’s skin over their life renders the ability to use fingerprints to identify the individual concerned.
There are two general types of fingerprint evidence that can be found at the crime scene or on objects related to it that is the visible and the latent fingerprint, but they are not mutually exclusive. This study is mainly concerned with latent prints.
Latent fingerprints are not often left in heterogeneous or protected environments, so there is the need to be able to detect their presence on different surfaces and after they have undergone the action of atmospheric agents or have been found, for example, on objects soaking in water of different types of impurities and sediments.
Small particle reagent (SPR) is a physical development technique for fingerprint detection on wet or moist surfaces.(1) There are many formulae of SPR available nowadays but the optimal formula hasnever been reported. In this study, the best SPR formula for detecting latent fingerprints on wet non porous surfaces was demonstrated.
In fact, there are many conditions of water that can contact with the fingerprint containing material surfaces, such as water from rain, roadside, effluent, canal or sea. The water from each source is quite different in its pH, salt types and levels and suspended particulate matter. However, the effect of the pH or salt concentration of the soaking solution upon the ability of each SPR to detect latent fingerprints has never been investigated. In this study, various types of surface samples soaked in each different solution (tap water, weak acid, weak base, and various concentrations of sodium chloride), which represents water from some of the different available sources, was used to evaluate the effect on latent fingerprint detection by SPR.