Methods in latent fingerprint discovery

Topics: Fingerprint, Cyanoacrylate, Light Pages: 8 (1603 words) Published: August 4, 2014

The Methods of Latent Fingerprint Discovery
Finding and Retrieving Latent Prints from a Crime Scene
Megan M. Anderson
Brevard Community College

This paper explores the methods of latent fingerprint discovery the finding and retrieving of latent prints from a crime scene. Here we will review how to find a latent print using alternative light sources and what those light sources are. We will also review the surface characteristics of evidence and the purpose of sequential processing. Making sure that the rights steps are taken when processing fingerprints so such evidence is not destroyed. Also we will go over the fingerprint development techniques, each of their uses and processes in finding and retrieving the fragile prints such as brush and powder, superglue fuming, small particle reagent, machine paper technique and others. This paper examines the techniques taught from Mark R. Hawthrone and Ross M. Gardner teachings and training.

The Methods of Latent Fingerprint Discovery
Finding and Retrieving Latent Prints from a Crime Scene
Everything we touch leaves a mark, an invisible unique, one of a kind pattern. These patterns are so unique that no two people have the same prints, not even identical twins. The patterns known as fingerprints identify who we are, where we have been, and what we have touched. These unseen prints we leave behind are called Latent prints, and for crime scene technicians they are the most fragile and valuable piece of evidence linking a person to a crime. The methods for finding and retrieving these prints are important. To take a wrong step and lose the print could cost you an important case. Here I will help you understand the methods used in finding and retrieving latent prints from a crime scene. How to find a Latent Print

There are a few ways that crime scene technicians use to make a print visible. Here I will list the equipment used in finding and retrieving latent prints. In choosing which technique to use in the development of a latent fingerprint sequential processing is important. We must use the least intrusive method to the most intrusive method, causing the least harm to the print first so we do not lose it. The order is as follows: 1. Available light 2. Powders 3. DFO 4. Ninhydrin and 5. Dye stain. Latent prints can be found on many different surfaces, and depending on the type of surface and its condition would be in your deciding factor to which step you may take in finding and preserving the latent print. After using your available light source you turn to an Alternative Light Source (ALS). There are a few ALS that are used in the findings of latent fingerprints, RUVIS and Blue Light. The Reflected Ultraviolet Imaging Systems (RUVIS) requires using the mirrored filter for examining undeveloped fingerprints. RUVIS operates using only UV/C (254nm) light, all other light is blocked from the imager by filter which means RUVIS can be operated under any lighting conditions. When searching for latent fingerprints the imager is held at a 45° angle and anywhere from 5 to 10 feet from the surface being examined with the imager lens set at ʄ/3.5. When viewed through the imager latent prints will appear a light silver or gray. Another ALS commonly used is Blue Light (485 to 530 nm). Using the wavelengths of 525 to 530 nm, in combination with an orange barrier filter, it is used for developing latent fingerprints with the use of the florescent powders. (Gardner, 2012) Surface Characteristics

Surface Characteristics define the fingerprinting methods used on scene. The nature of the surface to be printed and its current condition decide which techniques the crime scene technician can or should apply. There are four basic types of surfaces and they are: Porous surfaces, Nonporous smooth surfaces, Nonporous rough surfaces and Special conditions.

Porous Surfaces is any item that can absorb moisture like paper, cardboard, and untreated wood. The order of...

References: Gardner, R. M. (2012). Practical Crime Scene Processing and Invesigation. Boca Raton: CRC Press. Chapter 9
Hawthrone, M. R. (2009). Fingerprints Analysis and Understanding. Boca Raton: CRC Press. Chapter 5
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