FINGERPRINTS DAY 2 VISUALIZING AND LIFTING PRINTS September

FINGERPRINTS DAY 2: VISUALIZING AND LIFTING PRINTS September 11, 2018

TYPES OF FINGER PRINTS • Visible prints - prints that can be seen by the naked eye, made if the finger has touched grease, blood, paint, etc.

TYPES OF FINGER PRINTS • Visible prints - prints that can be seen by the naked eye, made if the finger has touched grease, blood, paint, etc. • Latent prints – prints that are invisible to the naked eye; formed from natural body oil and perspiration

TYPES OF FINGER PRINTS • Visible prints - prints that can be seen by the naked eye, made if the finger has touched grease, blood, paint, etc. • Latent prints – prints that are invisible to the naked eye; formed from natural body oil and perspiration • Plastic prints – 3 D negative impression of a fingerprint, made by pressing a finger into a soft, moldable material, such as putty, wax, glue, candy, etc.

COLLECTING FINGERPRINTS FOR EVIDENCE • Visible and plastic prints can often just be photographed for evidence. • Latent prints must be made visible to be observed & collected. After visualization, the print is photographed, lifted (if possible), and preserved.

VISUALIZING LATENT PRINTS There are three basic methods for visualizing latent prints 1) Oblique lighting & RUVIS • Most prints (even so-called latent prints) are at least partially visible and can be found by shining a flashlight or alternate light source along surfaces at an angle (oblique lighting). • UV lights and lasers make fingerprints fluoresce, and will reveal more prints than regular flashlights. • RUVIS (reflected ultraviolet imaging system) picks up reflected UV light & converts it into visible light. • Once found, the print can be photographed & lifted.

VISUALIZING LATENT PRINTS 2. Powder Dusting • Can be used to locate (over small areas), enhance, and preserve prints • Powder is lightly dusted onto a surface so as not to smear the prints. • The powder is lifted with clear tape and put onto backing paper. Powders come in a variety of colors, and some are magnetic. •

VISUALIZING LATENT PRINTS 3. Chemical Processing More effective than dusting on porous surfaces, such as paper, leather, styrofoam, etc. 3 chemical methods you need to know: • Ninhydrin • Iodine • superglue

LATENT PRINTS – CHEMICAL PROCESSING 1) Ninhydrin processing • Used on porous surfaces, including paper • Object is dipped in or sprayed with ninhydrin solution • Reacts with amino acids in print • Turns purple 2) Iodine processing • Used on valuable objects because it is impermanent • Evidence is placed in fuming chamber with crystal iodine • Iodine is trapped in oils of print to produce brown color • Will fade over time

LATENT PRINTS – CHEMICAL PROCESSING 3) Superglue (cyanoacrylate ester) • Evidence is placed in a fuming chamber with superglue OR is sprayed with a superglue fuming wand • The glue bonds to the print, forming a strong, stable, off-white impression. • Superglued prints are usually further treated with chemicals or powders to enhance the visibility of the print.

QUICK REVIEW 1. What would be the best way to look for latent prints over a large area? Oblique lighting, especially with alternate light source 2. What would be the best way to search for prints on a gun? Dusting and/or superglue fuming 3. What would be the best way to search for prints on a document? Ninhydrin spray 4. What is the main benefit of iodine staining? It doesn’t last – good for valuable items 5. What is a major benefit of superglue fuming? It creates durable impressions