Take out your notes (HW) and keep it at your desk. Monday, 12/16 Homework Quiz Take out your notes (HW) and keep it at your desk. Take a quarter sheet of scratch paper and put your name and class period on the top. You do not need to copy the questions, your responses do not have to be in complete sentences.

List the three types of fingerprints that are found at crime scenes. What does RUVIS stand for and what is it used for? What are three types of powders used to develop prints? Which type of chemical treatment was developed first? What is the first thing that a criminalist must do after visualizing a print but before any attempts are made to preserve it? When you are done: Put your quiz in the HW folder Keep your notes at your desk

Methods Of Detecting Fingerprints Objectives: Distinguish visible, plastic, and latent fingerprints. List the techniques for developing latent fingerprints on porous and nonporous objects. Describe the proper procedures for preserving a developed latent fingerprint.

Distinguish visible, plastic, and latent fingerprints. Visible prints: Made when the finger deposits a visible material such as ink, dirt, or blood onto a surface Plastic prints: Fingerprints impressed into a soft surface Latent (invisible) prints: Caused by the transfer of body perspiration or oils present on finger ridges to the surface of an object

Locating Fingerprints The method of visualization is determined by the type of surface being examined: Hard/nonporous surfaces: Powders and Super Glue fuming Soft/porous surfaces: Chemical treatment RUVIS (Reflected Ultraviolet Imaging System) Aims UV light onto a non-absorbent surface to help locate fingerprints Prints are then developed in the appropriate manner

List the techniques for developing latent fingerprints on porous and non-porous surfaces. Powders (grey/black, metallic, fluorescent) Chemical methods: Iodine fuming Ninhydrin Physical developer Super Glue fuming DFO Fluorescence

Powders Used mostly on dry, nonporous surfaces Applied with camel’s hair or fiberglass brush Powders adhere to the perspiration and oil residues left by the ridges Grey/black: Most common Used on lighter surfaces Magnetic: Less damaging to print Good for leather and rough plastics Fluorescent: Used in conjunction with UV light Prevents prints from being obscured by color of the surface

Iodine Fuming Oldest of the chemical methods Process: Iodine crystals and suspect material placed in a cabinet and heated Iodine goes directly from solid crystals to a gas (sublimation) when heated Vapors combine w/ the print to make it visible It is thought that the iodine combines with fatty oils or residual water in the fingerprint, but not known for sure Prints that are developed using iodine fuming are not permanent Can be extended by a month to a year with the application of a 1% solution of starch in water

Ninhydrin Process: Sprayed onto porous surfaces Frequently used on paper documents Purple/blue prints will appear w/in 1 to 2 hours after application Chemical reaction occurs with amino acids in the deposited perspiration

Physical Developer Silver nitrate-based liquid Used for visualizing latent prints undetected by previous methods Good for porous materials that may have been wet at one time Should be the LAST method used Washes away traces of proteins from an object’s surface Order of application: Iodine Ninhydrin  Physical developer

Super Glue Fuming Most useful for nonporous surfaces such as metals and plastics Process: Super Glue (cyanoacrylate) heated in enclosed chamber with suspect material Expose for about 6 hours Is developed when the glue adheres to the print and gives it a white appearance Fuming wands are available for more convenient development on larger surfaces Has been used to develop prints in small, enclosed areas such as the inside of a car

Super Glue Fuming

Fluorescence 1st – Discovered that fingerprints could be visualized by exposure to laser light 2nd – Fingerprints could be treated with chemicals that would induce fluorescence when exposed to laser light Chemicals that could be applied after development (zinc chloride after ninhydrin, rhodamine G6 after Super Glue fuming) 3rd – Lasers were no longer needed to induce fluorescence as it was now chemically induced, and high-intensity or alternate light sources could be used to visualize prints

Alternative light sources High-intensity Alternative light sources Quartz halogen Xenon-arc Focused using fiber-optic cables Can utilize several filters giving the flexibility to select different wavelengths of light Light-emitting diodes (LEDs) More portable

Additional Processing Information Chemical agents do not interfere with DNA tests Ideally, all processing and development of prints should be done in the laboratory and NOT at the crime scene

Preservation of Developed Prints Once developed, fingerprints must be preserved Before preservation  fingerprints must be photographed FIRST! Close-up of fingerprint Expanded shot for overall location of the fingerprint 2 possible procedures: Small objects: Preserve object w/ print in its entirety Cover print w/ cellophane Large objects: If developed w/ powder, lift print w/ adhesive

Digital Imagining For Enhancement Photographs are turned into digital files The larger the # of pixels, the more closely the file will resemble the real-world image Allows for the removal of background color interference More reliable hits in AFIS Easy creation of fingerprint comparison charts

Digital Imagining For Enhancement