LATENT FINGERPRINTS FLTCC Forensics

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Latent Prints Fingerprints are formed from material on the fingers that is pressed upon a surface. 1. Prints are also formed from oils secreted by the fingers. 2. Through the pores, perspiration is discharged and deposited on the surface of the skin. Once the finger touches a surface, perspiration, along with oils that may have been picked up by touching the hairy portion of the body, is transferred onto that surface.

Latent Prints A fingerprint is an individual characteristic; no two fingers have yet been found to possess identical ridge characteristics. The FBI has nearly 50 million fingerprint records in its computer database and has yet to find an identical image belonging to two different people.

Composition of Fingerprints Sweat 99.0-99.5 % water 0.5-1.0% solids 50% organic solids (mostly amino acids) 50% inorganic solids (NaCl and KCl) Contaminants Bodily fluids (blood, saliva, nasal secretions, semen, etc.) Oils and fats (sebum)

Three Types of Fingerprint Impressions Patent fingerprints – visible prints left on a smooth surface when blood, ink, or some other liquid comes into contact with the hands and is then transferred to the surface

Three Types of Fingerprint Impressions (continued) Plastic fingerprints – actual indentations left in some soft materials such as clay, putty, wax, or dust.

Three Types of Fingerprint Impressions (continued) Latent fingerprints – fingerprints that are invisible to the naked eye and caused by the transfer of oils and other bodily secretions onto a surface. They can be made visible by various different methods

Latent prints are impressions left by friction ridge skin on a surface, such as a tool handle, glass, door, etc. Prints may be collected by revealing them with a dusting of black powder and then lifted with a piece of clear tape. Did you know? Camel hair is the most common animal hair used to make fingerprint brushes. Now many brushes (like the one above) are made out of fiberglass.

Development of Latent Prints

Click the icon to view the Crime 360 Super Glue Video Some investigators use fluorescent powder and UV lights to help them find latent prints on multi-colored or dark surfaces. Magnetic powder can also be used to reveal latent prints. This type of powder works better on shiny surfaces or plastic baggies or containers. The cyanoacrylate fuming method (often called the super glue method) is a procedure that is used to develop latent fingerprints on a variety of objects. Ninhydrin is a chemical that bonds with the amino acids in fingerprints and will produce a blue or purple color. It is used to lift prints from surfaces such as paper and cardboard. Click the icon to view the Crime 360 Super Glue Video Top Left: http://www.stapletonandassociates.com/images/MagPowder.jpg Bottom Left: http://www.ok.gov/osbi/images/ninhydrin%20print.jpg Bottom Right: http://www.forensicsrus.com/images/SupergluePrint.jpg

Latent Prints A variety of techniques use powder and chemicals to develop latent fingerprints. A. Lifted fingerprints 1. Formed when a piece of adhesive tape is placed over a developed latent print and pulled away. 2. The latent print adheres to the tape and then the tape is placed upon a glossy white or black “latent lift backer” card.

Latent Prints 3. Photography is used during the development and lifting process.

Latent Prints Techniques range from chemical methods such as powders and iodine fuming to the use of laser light. Fingerprint powders The powders, when applied lightly to a nonabsorbent surface with a camel’s-hair or fiberglass brush, readily adhere to perspiration residues and/or deposits of body oils left on the surface.

Latent Prints – Fingerprint Powder with Fiberglass bush

Latent Prints – Fingerprint Powders Experienced examiners find that gray and black powders are adequate for most latent-print work 1. Gray powder, composed of an aluminum dust, is used on dark colored surfaces. It is also applied to mirrors and metal surfaces.

Latent Prints – Fingerprint Powders 2. The black powder, composed basically of black carbon or charcoal, is applied to white or light colored surfaces. 3. Fluorescent powders are also used to develop latent fingerprints. These powders fluoresce under ultraviolet light.

Fingerprint Powders Applied lightly to a nonabsorbent surface with a soft brush. They readily adhere to sweat residues and/or deposits of body oils left on the surface. Investigators need to prevent damaging the print when trying to develop it Did you know? Camel hair is the most common animal hair used to make fingerprint brushes. Now many brushes (like the one above) are made out of fiberglass.

Fingerprint Powders (continued) Gray and black powders – the most common, chosen to make the best contrast with the surface Fluorescent powders – used to photograph latent prints on multi-colored surfaces. They fluoresce under ultraviolet light.

Fingerprint Powders (continued) Magnetic powder – magnetic powders are applied with a magnetic brush Allows for very delicate application of powders, decreasing chances of scratching prints with bristles

Things to Consider about Fingerprint Powders… Fineness The powder must be fine enough to show the detail of the fingerprint. Finer powders would be theoretically capable of displaying greater detail than coarser powders. Adhesion The powder must display the right level of adhesion, so that it will adhere to the residue of the fingerprint (often oils) and not adhere to the rest of the surface where it would obscure the view of the print. When a powder coats a surface, this is known as 'painting'. Sensitivity Sensitivity is related to adhesion, and is how well the powder adheres to a surface. For example, aluminum flake is more sensitive than aluminum powder, but greater sensitivity is not always desirable. Color The fingerprint powder must be a suitable color for the surface in question. Flow To a lesser extent, it is important that the powder can flow, and does not 'cake' into a solid block, which would render it useless.

Fingerprint Chemicals (continued) DFO (1,8-diazafluotrn-9-one) – newer replacement chemical for ninhydrin. It is 2.5 times more sensitive than ninhydrin. Rhodamine 6G is a fluorescent dye that may be used after cyanoacrylate fuming to visualize latent prints under laser light. Once fluorescent dyes are applied, fingerprints can then be visualized using an Alternate Light Source (ALS) in an effort to enhance ridges and minimize background interference

Fingerprint Chemicals (continued) Gentian violet (or crystal violet) – used for developing latent prints on the adhesive side of tape. An aqueous solution of crystal violet is sprayed directly onto the adhesive. Wetwop is another solution developer that can be used on adhesive surfaces.

Fingerprint Chemicals (continued) Amido Black – protein dye stain that can develop faint bloody fingerprints on porous and nonporous surfaces. Blood must be swabbed prior to amido black application for any DNA analysis

Fingerprint Chemicals (continued) LCV (Leuco Crystal Violet) – a protein stain spray that can develop faint or invisible bloody fingerprints on non-porous surfaces

LUMINOL A chemical that reacts with hemoglobin to produce the phenomenon of chemiluminescence (same as fireflies!) Can be sprayed where nothing is visible. Under UV light, blood or bodily fluids glow

Other Chemical Developers… Sticky-side powder – paste made with powder that is used after cyanoacrylate fuming and on the sticky side of tape Basic Yellow 40 – another fluorescent technique for nonporous surfaces or post-cyanoacrylate fuming DAB – Diaminobenzidine formula – another blood enhancement technique Small particle reagent – useful on wet surfaces such as plastic bags or coated surfaces – adheres to the fatty deposits in fingerprints

Preservation of Developed Latent Prints Photograph!! Covering the print to preserve it in its entirety (if on a small object) Lifting the prints with adhesive tape and placing the tape with prints on a card with labels

Chemical Development: Fingerprints > Analysis Chemical Development: Iodine Fuming Iodine sublimes (solid → gas) Iodine reacts with lipid components; becomes trapped in the print. Fuming wand or chamber Dirty Brown Color

Latent Prints – Iodine Fuming Of the several chemical methods used for visualizing latent prints, iodine fuming is the oldest. Iodine is a solid crystal that, when heated, transforms into a vapor without passing through a liquid phase; such transformation is called sublimation.

Latent Prints – Iodine Fuming Most often, the suspect material is placed in an enclosed cabinet along with iodine crystals. As the crystals are heated, the resultant vapors fill the chamber and combine with constituents of the latent print to make it visible.

Latent Prints – Fuming Cabinet

Latent Prints – Iodine Fuming Iodine prints are not permanent and begin to fade once the fuming process is stopped. Must photograph immediately on development. Prints can be fixed with a 1 percent solution of starch in water, applied by spraying.

Fingerprint Chemicals (continued) Iodine fuming – one of the oldest latent print development methods. Solid iodine crystals sublimate and the vapor will react with fatty oils and some sweat residue. Iodine prints are not permanent and will begin to fade once the fuming process is stopped. Can be used on porous and nonporous surfaces

Fingerprint Chemicals Ninhydrin – reacts with amino acids in sweat to form purple-blue prints. A 0.6% solution (in ethanol) is sprayed onto porous surfaces such as paper.

Chemical Development: Fingerprints > Analysis Chemical Development: Ninhydrin Reacts with amino acids; purple color Painted or sprayed on area Heated to react

Latent Prints - Ninhydrin For most fingerprint examiners, the chemical method of choice is ninhydrin. Its extreme sensitivity and ease of application have all but eliminated the use of iodine fuming. Ninhydrin is a chemical reagent used to develop latent fingerprints on porous materials by reacting with amino acids in perspiration. It is commonly sprayed onto the porous surface from an aerosol can.

Latent Prints - Ninhydrin The development of latent prints with ninhydrin depends on its chemical reaction to form a purple-blue color with amino acids present in the trace amounts in perspiration. Generally, prints begin to appear within an hour or two after ninhydrin application.

Latent Prints – Physical Developer Physical developer is a silver nitrate-based reagent formulated to develop latent fingerprints on porous surfaces. This technique is very effective for developing latent fingerprints on porous articles that may have been wet at one time.

Fingerprint Chemicals (continued) Physical Developer – silver nitrate-based liquid reagent used on porous surfaces. It is often used as the last resort because it destroys protein. Cyanoacrylate (superglue) fuming – developed in 1982 by Japanese Police. It is used on a variety of materials not only to visualize latent prints, but also to semi- permanently affix them to the surface. Works best on nonporous surfaces. Can be developed further with powders or fluorescent dyes

Chemical Development: Fingerprints > Analysis Chemical Development: Super glue fuming Fumes with heat or base (NaOH) Fumed in cabinets Off-white print

Latent Prints – Super Glue Fuming Super glue fuming is a technique for visualizing latent fingerprints on nonporous surfaces by exposing them to cyanoacrylate vapors; named for the commercial product Super Glue.

Latent Prints – Super Glue Fuming Super glue is placed on absorbent cotton treated with sodium hydroxide. The fumes can be fumes can also be created by heating the glue. The fumes and the evidential object are contained within an enclosed chamber for up to six hours.

Latent Prints – Super Glue Enclosed Chamber

A hand held fuming wand uses disposable cartridges containing cyanoacrylate

Wand can be used at Crime Scene to develop prints

Latent Prints – Super Glue Fuming Super glue is approximately 98 to 99 percent cyanoacrylate ester, a chemical that interacts with and visualizes a latent fingerprint. Development occurs when fumes from the glue adhere to the latent print, usually producing a white-appearing latent print.

SUPERGLUE FUMING https://www.youtube.com/watch?v=FkcSkADVMIM UNT in partnership with TEA, Copyright ©. All rights reserved.

Chemical Development: Fingerprints > Analysis Chemical Development: Ninhydrin and super glue prints can be further processed: Dusted Chemically treated to fluoresce (using laser or alternative light)

Preservation of Developed Prints Once the latent print has been visualized, it must be permanently preserved for future comparison and possible use in court as evidence. A photograph must be taken before any further attempts at preservation.

Factors Affecting Fingerprints Age – thinner epidermis, flattening of dermal papillae, creases, etc. Fine ridge structure – less skin contact leads to a spotty appearance. Stimuli – sweating can be due to warmth, exertion, fever, drugs, anxiety, tension, pain, or spicy foods. Occupational and medical condition – teaching, and other positions in which a person handles or shuffles papers, can cause fine ridge structure.

Factors Affecting Fingerprints (continued) Transposal factors Receiving surface texture Contaminants on the hands Contaminants on the receiving surface The manner of contact The amount of pressure Environmental factors Temperature Humidity Handling

Trends with Fingerprints It is NOT possible to determine the age, sex or race of an individual solely from their fingerprints. However: Statistically in young adults, friction ridges of women are significantly finer than those of men. Fine ridges may be found in the very young and the very old. Manual labor tends to strengthen ridges. Women tend to perspire at a lower rate than men. Sodium chloride (NaCl) is lower for women. Creases are more common in women's FPs.

AFIS Database of fingerprints taken from arrests and unknown fingerprints found at unsolved crime scenes Investigators enter both known and unknown prints and identify the minutiae When an unknown print is entered into AFIS, the minutiae are identified and the computer crosses them with known offenders THE INVESTIGATOR MAKES THE LAST DECISION on a match

Modern Fingerprint Analysis Fingerprints Modern Fingerprint Analysis Computer system stores patterns and minutiae of prints AFIS: automated fingerprint identification system

http://www.youtube.com/watch?v=ZKi1CKTRCQM&feature=r elated AFIS http://www.youtube.com/watch?v=ZKi1CKTRCQM&feature=r elated UNT in partnership with TEA, Copyright ©. All rights reserved.

Latent print development https://www.youtube.com/watch?v=tqFzVfPRd5s UNT in partnership with TEA, Copyright ©. All rights reserved.

Collection of prints: Tape lift: Tape placed over developed print Fingerprints > Collection Collection of prints: Tape lift: Tape placed over developed print Tape then placed on white card.

Fingerprints > Collection Collection of prints: Sometimes a photograph will be the only permanent record.

Latent print comparison https://www.youtube.com/watch?v=j2BcxTW_EV Q#t=90 UNT in partnership with TEA, Copyright ©. All rights reserved.