Latent fingerprint development
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This document discusses latent fingerprint development and analysis techniques used in criminal investigations. It begins with definitions of fingerprints and latent prints. It then discusses the chemical composition of latent print residue and why fingerprints are important evidence. The document outlines where latent prints can be found and the contents of a fingerprint field kit. It describes both physical methods like powdering and chemical methods like silver nitrate and ninhydrin staining to develop latent prints and make them visible for analysis.
Latent fingerprint development
- 1. By : TEJASVI BHATIA Latent Fingerprint Development
- 2. CONTENTS Definitions Latent print residue Why are fingerprints important in Criminal Investigation? Where are latent fingerprints found? Items to be included in a fingerprint field kit Methods of development I. Physical methods II. Chemical methods Conclusion References
- 3. DEFINITIONS Fingerprints are the distinctive ridge outlines which appear on the bulb on the inside of the end joints of the fingers and thumbs. Latent fingerprints have been defined as the markings of oily matter or perspiration from the skin glands, left upon any surface which the hands and fingers may have touched. These are invisible , and require developing or “disclosing” treatment to make them visible.
- 4. LATENT PRINT RESIDUE Latent fingerprints are composed of several chemicals exuded through the pores in the fingertips and left on virtually every object touched. The primary component of latent fingerprints is sweat. Sweat is 99% water, and will dry after a fairly short period of time. The other components of latent fingerprints are primarily solid and can remain on a surface for a much longer period of time. They include amino acids, glucose, lactic acid, peptides, riboflavin, proteins, lipids, potassium, sodium, calcium, and numerous others.
- 5. WHY ARE FINGERPRINTS IMPORTANT IN CRIMINAL INVESTIGATION? The potential aids offered to law enforcement by fingerprints are numerous as:- I. Fingerprints are unique. No two individuals have identical fingerprints. II. Fingerprints do not change throughout the life span of an individual. The finger markings on some lethal weapon often determine whether the act was that of suicide or murder. Latent fingerprints are found on various objects that come in contact with a suspects hands at a crime scene. As these are unique ,a suspect can be identified as the perpetrator of a crime.
- 6. WHERE ARE LATENT FINGERPRINTS FOUND? I. Smooth, Non-Porous surfaces II. Rough, Non-Porous surfaces III. Paper and Cardboard IV. Plastic Packaging Material V. Soft Vinyl (PVC), Rubber, and Leather VI. Metal (Untreated) VII. Unfinished Wood VIII. Wax and Waxed Surfaces IX. Adhesive-Coated Surfaces
- 7. FINGERPRINT FIELD KIT Fingerprint powders 2 brushes for dark and light powders 2 feather dusters for light and dark powders Latent print lifting material Mounting material Fingerprint record cards Supply of cards for mounting latents(black and white) Fingerprint ink Glass plate for inking
- 8. Complete post mortem outfit for printing corpses:- I. Pair of scissors II. Pair of rubber gloves Notebook Flashlight Atomizer for applying powder Atomizer for applying chemicals
- 9. METHODS OF DEVELOPMENT These include:- Physical methods Chemical methods
- 10. PHYSICAL METHODS POWDERING METHODS This method of developing latent fingerprints is based on the simple physical phenomenon of adhering. The powder substances when applied to the latent fingerprints in a proper and systematic manner ,adhere to the secretions left on the object bearing latent fingerprints. The most commonly used powders are black and grey powders. Black powders are used for developing prints on white or light colored surfaces and grey powders are used on dark colored surfaces to give maximum contrast.
- 11. FINGERPRINT DEVELOPMENT GREY POWDER BLACK POWDER
- 12. FLUORESCENT POWDERS When the latent impressions are to be developed on a multicolored surface, the use of powder of one color does not prove useful because of lack of contrast of the developed print against multicolored background. Such type of impressions are developed with fluorescent powders which can be applied like other powders. The prints developed with fluorescent powders glow under ultraviolet light and they can be photographed on an ordinary film. These powders are available in a variety of colors like green, red and yellow.
- 13. FINGERPRINT DEVELOPMENT •Background surfaces containing multiple colours are often processed with fluorescent powder, as the brilliance of the powder will contrast with the background allowing for detailed photography. Orange Fluorescent Powder fluoresces with a forensic light source under Ultraviolet or blue wavelengths. Powder should be applied with an Orange Feather Brush.
- 14. XEROX TONERS The black colored Xerox toners in powder form can also be used to develop latent fingerprints. these can also be fixed(rendered permanent ) on the object by applying some heat.
- 15. METHOD OF DEVELOPMENT The selected powder is lightly applied to the suspected surface with a fine fingerprint brush. The brush is applied firstly in one direction and then in the other direction and when the ridges start appearing the brushing is done in a way that its motion follows the flow of ridges. When sufficient powder adheres to the impression ,the excess powder is carefully brushed away with a light soft touch. When the object is small and movable ,it can be tilted to remove the sprinkled fingerprint powder. The excess powder on the print is removed carefully by soft and light touches of the brush.
- 16. LIFTING POWDERED PRINTS When the developed fingerprints cannot be readily photographed due to physical location of such prints, they have to be lifted from that surface for comparison purposes and permanent recording. The fingerprint lifters include photographic paper, transparent tapes and opaque lifters. The sticky surface of the fingerprint lifter is pressed against the developed print in a careful manner. When the surface of the lifter has been uniformly pressed over the developed print, it is carefully drawn off from the object and mounted on a suitable card.
- 17. LIFTING BY TRANSPARENT TAPES After applying the tape ,the fingerprint is lifted and mounted on a black or a white card included in the fingerprint kit.
- 18. IODINE FUMING METHOD This method depends on the principle that when the oily and fatty deposits of the latent impressions come in contact with the iodine fumes produced by subjecting iodine crystals to slight heat, they become visible in yellowish brown color. These prints are however not permanent, and should be photographed before they begin to fade and are at their full intensity. Iodine fuming can be carried out in a closed chamber or with the help of an iodine fuming pipe.
- 21. CHEMICAL METHODS These methods include:- I. Silver nitrate method II. Ninhydrin method III. Osmic acid method
- 22. SILVER NITRATE METHOD This method is based on the fact that the sodium chloride of the deposited perspiration in the latent impression reacts with silver nitrate solution to form silver chloride which is light sensitive. When exposed to light, it breaks into its component silver and chloride. The developed prints are reddish brown in color. A 5% silver nitrate solution is generally used for this purpose.
- 23. NINHYDRIN METHOD The development of latent prints with ninhydrin is based on the chemical reaction of ninhydrin with amino acids which are present in perspiration causing the formation of purple reddish stains that render latent impressions visible. Normally 1.5% solution of ninhydrin is used.
- 25. OSMIC ACID METHOD This method is based on the reaction of osmic acid vapors with oily matter of the latent impressions. When osmic acid vapors come in contact with sebaceous matter, it is reduced to metallic osmium which is blue colored. The solution is prepared by dissolving 3 grams of osmic acid in 100cc of carbon tetrachloride, ether or ethyl alcohol.
- 26. CONCLUSION It has been aptly said that the criminal’s own hand is his greatest enemy. As the most important aid to the sense of touch, the hand and fingers meet frequently with the surrounding objects and surfaces, thus producing evidential markings that may serve either to condemn or to vindicate the accused.
- 27. REFERENCES Lee, Henry & R.E. Gaensslen. Advances in Fingerprint Technology, 2nd Ed. CRC Press. Boca Raton, Florida. Bridges , B.C. practical fingerprinting . Funk and Wagnallas company, New York,1942 http://www.onin.com/fp
- 28. THANK YOU