Latent prints are a sort of physical evidence that is both valuable and common. Fingerprints have provided important evidence in countless serious criminal cases. Fingerprints left on the scene of a crime contain not only the suspect’s sweat, but also traces of substances touched by the suspect. However, fingerprint recovery can be difficult even impossible in some cases.
Friction ridges on human fingers, palms, and soles of feet form latent prints, which are impressions made by the ridged skin.
In order to make identifications or exclusions, examiners compare latent prints to known prints of individuals. Examiners can compare two prints and establish whether two friction ridge impressions came from the same source because to the uniqueness, permanence, and arrangement of the friction ridges.
In the identification and development of latent prints, a variety of procedures are used, including the introduction of chemicals, powders, lasers, alternate light sources, and other methods to identify. Experts may also conduct microscopic studies in order to make conclusive comparisons when a latent print is of low quality and amount of detail.
fingerprints begin to form before birth. Fingerprints are tiny ridges on the tip of finger. They are basically the folds of the outer layer of skin, which is know as epidermis. The “fingerprint” forms because of the skin oil or dirt which ridges leave on contacted surfaces.
The finger leaves traces of sweat and other substances such as; amino acids, sebaceous, salts, urea and fatty acids, that the suspect may have touched. These substances deposit in the pattern of ridges characteristic of the fingertips of the dispenser. Most fingerprints are invisible to the naked eye and require a chemical development process to make them visible.
Latent fingerprints might also be found in wet and moist environments. These surfaces can be wet or moist due to various reasons, such as; washroom surface, rain, canal, or sea water.
Different chemicals can be used to detect and analyse latent, non-visible fingerprints. For instance, specific powders (such as, magnetic, or fluorescent powders) are put to the exhibit’s surface and adhere to the trace’s contents. These powders, however, cannot be utilised to detect latent prints on damp/moist surfaces because water drops would cause the fine powder to accumulate.
Detection of fingerprint on wet surfaces is quite a challenge. The best methods for developing prints on wet surfaces are:
👉 Physical Developer works best with porous substrates.
👉 Powder in suspension is usually used to treat non-porous substrates. e.g., Small Particle Reagent or Wet Powder.
SPR (Small Particle Reagent) is a technology that uses the reaction between fatty-acid residuals in traces and hydrophobic tails of certain reagents to identify latent fingerprints left on wet or moist surfaces. By spraying a solution containing small coloured particles (White, Black, UV-active) on the exhibit’s moist surface, SPR makes fingerprints visible. These particles cling to endogenous secretions, allowing the print to be detected. The excess spray should be wiped away with distilled water after a print is apparent. The print can be obtained with a regular gel lifter instantly after this process. Visible fingerprints should be photographed immediately especially if they are on rough and textured surfaces.