Does a fingerprint generally change during your lifetime...
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} Does a fingerprint generally change during your lifetime? } What is another name for ridge characteristics? } Name and explain the 3 classes of general patterns for fingerprints.
Transcript of Does a fingerprint generally change during your lifetime...
}Does a fingerprint generally change during your lifetime?
}What is another name for ridge characteristics?
}Name and explain the 3 classes of general patterns for fingerprints.
}Computer scans and digitally encodes fingerprints
}Converts fingerprint images into digital minutiae of a geometric pattern
}Makes thousands of fingerprint comparisons in seconds
1. Latent prints- hidden prints, invisible print impressions caused by perspiration on the ridges of the skin coming in contact with a surface and making an invisible impression on it. (perspiration contains water, salt, AA or oils)
2. Plastic prints- ridge impressions left on a soft material like putty, wax, soap or dust.
3. Visible prints- made by fingers touching a surface after the ridges have been in contact with a colored material like blood, paint, grease or ink.
}The method used for analyzing prints depends on the type of surface to be examined, how the prints were left, and the quantity of material left behind.
◦Hard and nonabsorbent (glass, mirror, tile, and painted wood) use powders or Super Glue fuming.◦Soft and porous (papers, cardboard, and cloth) use chemical treatments
}Super Glue Fuming Video
RUVIS- Reflected UltraVioletImaging System, can locate prints on nonabsorbant surfaces without chemical or powder treatments
}Apply with camel’s hair or fiberglass brush
}Adhere to perspiration or body oils left on surface
}Use powder that will give best color contrast with surface being dusted
}How To Dust for Fingerprints Video
}Carbon powder- use for white or light-colored surfaces
}Lanconide powder- use for black surfaces
}Aluminum powder- use for hard or dark-colored surfaces, mirrors and metals
}Magnetic powders}Fluorescent powders- need UV light
Iodine- solid crystal that directly changes to a vapor when heated (sublimation)
}Latent print becomes visible but fades once fuming stops (not permanent)
}Take photographs immediately
Super Glue- (cyanoacrylate) }Used for nonporous surfaces, like metals, electrical tape, leather and plastic bags
}Place super glue in an air-tight, heated chamber with the evidence for up to 6 hours
}Prints turn white
Ninhydrin- turns purple-blue with AApresent in perspiration
}Spray/wipe this onto porous surfaces}Prints can take up to 48 hours to appear
}Ninhydrin Video
Silver Nitrate- (Physical developer)} Used when other methods have not found latent prints
}Method fault- can wash away proteins and change evidence, SO USE AS LAST RESORT.
}Photograph- use camera with close up lens or fixed focus photograph on a 1:1 scale, camera held flush against print’s surface.
}Need photograph of overall view of print’s location with respect to other evidential items at crime scene
} If object is small, it can be transported without destroying the print (cover print with cellophane)
} If prints are on large, immovable objects, then use lifting technique(adhesive tape and powder and place on labeled card)
}Can enhance lifted prints with computers (print picture is converted into a digital file)
} Beating Fingerprints - Mythbusters
