Development of Latent Fingerprints
- 1. Development of Latent Fingerprints Prepared By:- Mohd Hamza MA Semester 2 (Forensic Science)
- 2. Chance Prints • To start with further discussion we need to be first familiar with to as to what is Chance Print. • Chance Prints are the fingerprints that are recovered from the scene of crime as the suspect comes in contact with the various surroundings and objects of the crime scene. • There are mainly three types of Chance Prints that we generally encounter.
- 3. Visible Prints • During the course of time the suspect’s hands may get contaminated with a number of external contaminations like powder, soil, grease, paint or blood. • When Palms stained with such contaminations are pressed against any surface the ridge patterns of the palms get imprinted upon that surface acquiring the inking from the contaminating agent.
- 4. Plastic Prints • When suspect’s hands are pressed against soft or plastic substances like butter, wax, wet painted surface, plastic explosives, clay etc. The ridge pattern’s of the respective palm get imprinted upon that surface in a three dimensional format and occur as negative to the ridges.
- 5. Latent Finger Prints • During the course of crime the culprit’s hands get exposed to oil, dirt and grease from touching the tools skin or hair also it’s a common tendency of a human being to get nervous while committing a wrong deed which leads to excessive perspiration. • The contents of the perspiration (Water, Salts and Amino Acids) along with the external contamination happen to leave a thin film of ridge patterns upon any surface the perpetuator’s hands come in contact with. • These patterns are invisible to unaided eyes and if visible may be unrecognizable and need development. • In some cases of professional crimes gloves may be used in that case fingerprints can be recovered from the gloves if found.
- 6. Development of Latent Fingerprints • There are various Physical and Chemical methods employed to develop latent fingerprints. • Physical Methods rely on the ability of reagents used to adhere to the materials of prints without fusing into them. • Chemical Methods rely on the ability of reagents to react with the contents of the fingerprints (Amino Acids, Salt, External Contaminants and Water)
- 7. Development Physical Chemical Powder Laser Electromagnetic Image Enhancement FumingReagent Bloody Greasy • Black (Lampblack, Graphite, Charcoal) • Grey (Chalk + Mercury) • White (Titanium Oxide + Zinc Oxide + Gum Acacia • Red (Powdered resin of a palm fruit) • Silver (Aluminium Dust) • Fluorescent (Anthracine + Rhodamine-B) • Silver Nitrate • Ninhydrine • Osmium Tetroxide • Iodine • Cyanoacrylate • Metal Fumes • Amino Black • DFO • Fluorescence • Sudan Black • Physical
- 8. Powder Method • It is the oldest and most widely used method and can be considered as quite convenient. • Should be adhesive to the contents of the fingerprints and of contrasting colour to the background. • Squirrel hairbrush or camel hair brush are used. • Brush strokes should be polite and sparing amount of powder should be used for effective results. • Generally useful for non porous surfaces.
- 9. The following powders are used Black Powder (Charcoal, Graphite, Lampblack) • Excellent for chinaware and smooth surfaces. • If to be applied to porous surface should be used with Magnesium Oxide. Red Powder (powdered resin of palm fruit) • Excellent for paper with fresh prints and treated with heat. Grey Powder (Chalk + Mercury) White (Titanium Oxide, Zinc Oxide and Resin Acacia) • Excellent for glass, silverware and plated ware. Silver (Aluminium Dust) • Excellent for cellophane, feather, polished, painted and varnished surface. Fluorescent Powder (Anthracine and Rhodamine-B) • Useful for coloured surfaces. Magna Powder • Useful in all except metals.
- 10. Laser • Fingerprints contents like ink, blood, oil and other substances when placed under laser along with suitable filter show various fluorescence. • Continuous Wave Ion Argon Laser is used. • It is useful even in very old prints even as old as 10 years Electromagnetic • Fine lead particles are spread over skin. • X-Ray is radiated passing through various filters like copper and aluminium to filter out soft components. • Neutrons emitted from lead when it comes in contact with X rays leave an imprint of X ray film.
- 11. Image Enhancement • High resolution cameras are used to capture visuals of the prints and are exported to a computer. • Computer can recognize or more shades of greys than naked eyes. • Variations in colour schemes are processed in the computer and further enhanced to give a clear picture of the prints. • This is latest technology and very useful for prints over textured surface where patterns or the background interfere with the ridge pattern.
- 12. Fuming Method- Useful for porous materials like cardboard, paper and wood, etc. Iodine Method • Fatty and oily substances of finger prints absorb iodine to give a brown tinged print. • It can be useful for development from skin such that a silver plate is pressed against the skin portion bearing possible prints and exposed to strong light to give black prints.
- 13. Cyanoacrylate Fumes • React with amino acids to give chalky white prints Metal Fumes • When metals like gold are evaporated in vacuum chambers it gets deposited on the prints.
- 14. Chemical Reagents Useful in old prints on both porous and non porous surface Ninhydrine Method • When Ninhydrine comes in contact with amino acids of perspiration it gives a pinkish purplish print. Silver Nitrate • Reacts with Sodium Chloride present to give Silver Chloride which is a highly photosensitive substance. • It turns black when exposed to light. Osmium Tetroxide • Reacts with oils and fats to give black prints due to formation of Osmium.
- 15. Bloody Fingerprints • Often available at violent crime scenes. • Although most of the tests don’t differ but few are exclusive for them. • But before applying these methods blood should be first recovered as biological evidence for DNA extraction and other tests. DFO • 1,8 Diazaflourene 9 One when exposed to blood gives fluorescent or coloured prints Amino Black • Develop black fingerprints when exposed to blood. Fluorescent • Blood absorbs light and thus prints can be revealed as dark patterns if background is illuminated.
- 16. Greasy- Found on drink cans, automobiles, milk cartons as sticky deposits. Sudan Black • Ethanoic solution of a dye called Black-3 gives black print when introduced to greasy latent prints. Physical Method • Silver Nitrate along with an iron coupled redox & 2 Detergent Molecules are used. • They react with Sodium Chloride in small quantity of perspiration to give greyish black prints. • For non-porous Gentian Violet is used which gives a pinkish purple or violet prints.
- 17. Following points should be kept in mind before applying any methods. • The surface of application (porous, non-porous). • The possible contents of the prints. • Any contamination that can linger or enhance the prints. • Methods should not have adverse effects on evidence at the beginning of sequence. • External factors like exposure to water. • Possible time i.e. of prints. • Viscera available should first be recovered before starting examination. • Importance and context of case.
- 18. Thank You