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NCJRS Abstract

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NCJ Number: 98861 Find in a Library
Title: Latent Print Detection by Laser
Journal: FBI Law Enforcement Bulletin  Volume:54  Issue:6  Dated:(June 1985)  Pages:1-8
Author(s): J E Ridgely
Date Published: 1985
Page Count: 8
Sponsoring Agency: National Institute of Justice/
Rockville, MD 20849
NCJRS Photocopy Services
Rockville, MD 20849-6000
Sale Source: National Institute of Justice/
NCJRS paper reproduction
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United States of America

NCJRS Photocopy Services
Box 6000
Rockville, MD 20849-6000
United States of America
Document: PDF
Language: English
Country: United States of America
Annotation: This article describes the FBI's laser latent print detection system and its use, and evaluates its effectiveness relative to other latent fingerprint detection methods.
Abstract: The nucleus of the system is a Spectra Physics Model 171-19, continuous wave, 18-watt argon-ion laser with a Model 270 power supply. The unit has a spectral range of 457.9 to 514.5 nm. Optics permit single and multiline operation in the blue-green portion of the spectrum. The laser head is equipped with an optional fiber interface to permit limited portability of the laser beam, and an optical fiber cable can be used for items too large for the staging area. The laser beam is used to fluoresce certain properties of perspiration, body oils, and foreign substances in latent print residues. Detection occurs when residues absorb the laser light and re-emit it in wavelengths longer than the illuminating source. A comparative evaluation of laser and conventional latent print detection methods found that latent prints were developed in 242 actual criminal cases with fingerprint powders, 930 cases with ninhydrin, 1 case with silver nitrate, 1 case with idodine fumes, and 214 cases with laser. In the laser cases, latent prints were not developed in any instance by subsequent application of fingerprint powder or chemicals. In addition to excitation of latent print residue, the laser has proven valuable in photographing visible, treated and untreated latent prints, producing higher quality products and increasing the latitude of photographic procedures. While the laser system will not replace conventional detection methods, it provides a supplement of value in detecting previously unobtainable latent prints.
Index Term(s): Crime laboratory equipment; Equipment evaluation; Evidence identification; Investigative techniques; Latent fingerprints
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