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Physical Evidence

Physical Evidence. Prints and impressions (tires, shoes, fingers). Wrongful arrest,convictionFBI Portland case.wmv DNA and phys evidchurch fires tire.wmv. Footprint at scene said to Match Avila’s OC Register , 4/5,05.

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Physical Evidence

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  1. Physical Evidence Prints and impressions (tires, shoes, fingers) \Wrongful arrest,conviction\FBI Portland case.wmv\DNA and phys evid\church fires tire.wmv

  2. Footprint at scene saidto Match Avila’s OC Register, 4/5,05 • Samantha was kidnapped in July 2002 whileplaying in front of her home with a friend. Herbody was found the next day. She had beensexually assaulted, then suffocated. • Sgt. Robert Kennedy, an RCMP expert onfootprint comparison, testified that afootprint found near the body haddistinct characteristics that matched Avila’s right foot. • Mark Johnson, an Orange County Sheriff’s crime lab forensic specialist, testified that shoeprints found near the body had a pattern matching a size 12 Fila Disrupter tennis shoe. • Mark Johnson also testified that tire prints found at the scene were of the same size and design as the Michelin tires on Avila’s 1994 Ford T-Bird.

  3. Prints • Prints are made when an object deposits a two-dimensional pattern • Patterns are deposited by raised sections, or “ridges” • Deposits can be visible or latent • Latent prints become visible through development • Visible or developed prints are photographed and (if possible) lifted • Given sufficient “points of ID” prints can be individually matched to a person or object

  4. Impressions • Impressions are made when pressure from an object creates a three-dimensional image on a soft surface • Impressions should FIRST be photographed; then, if possible, cast • Given sufficient “points of identification”, impressions can be individually matched to a person or object • Unusual impression: pattern of pedestrian’s clothing on vehicle paint

  5. Shoes • Class characteristics • Identify brand and model from outsole designfeatures • Computer-assisted matching • Individual characteristics • “Points” of comparison, from questioned to known

  6. Tires Impression in mud compared to suspect’s tire • Class characteristics • Identify tire brand and model • Identify vehicle brand and model • Identify vehicle brand and model from track (width) and wheelbase (length) • Individual characteristics • May identify specific tire from wear and damage (“points of identification”) • Church fires (March 2006) • Agents found tracks from a BF Goodrich all-terrain tire • Witnesses to several fires described a Toyota SUV • Agents checked tire dealers for purchases, came up with suspect’s mother • Father said son confessed to him Advanced Imaging and Analysis.com

  7. Fingerprints • What are they? • Outlines of ridges where sweat glands are present • How are they deposited? • Inked • Stained or dirty hands • Impressions on soft materials (“plastic prints”) • Body secretions (sweat and other chemicals)

  8. Developing fingerprints • Making visible (“developing”) • Special light sources (u.v., laser) • Dusting with materials that adhere to body secretions • Light & fluorescent powder • Chemicals to darken body secretions • Ninhydrin • Superglue fuming  • Photograph before lifting • Special conditions • Fingerprints on paper • Fingerprints on bodies • Fingerprints on greasy surfaces

  9. Island Dot Bifurcation Ridge ending Identification • Common patterns • Loop • Whorl • Arch • Common minutiae • Islands • Dots • Bifurcation • Ridge endings policensw.com

  10. Comparison • Compare pattern (loop, arch, whorl) • If similar, then compare minutiae (where ridges start, stop and separate) • Islands, dots, bifurcations, ridge endings • Set number of points (6-15) must be identical in type and location with known print to make an identification • “Locations” found as on a map and by counting ridges policensw.com

  11. AFIS • Old system required having a suspect in mind, with a 10-print card on file • Questioned print compared to card • New system – AFIS • Digitizes 10-print cards from arrested persons • Digitizes prints recovered at crime scenes • Compares both, looking for possible matches • Makes suggestions • Final match must be done in the conventional way, by comparing minutiae

  12. Fingerprint comparison not foolproof • Subjectivity • Sloppy work • Pressures toproduce • FBI arrest ofMuslim attorneyin Portland

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