Footprint Evidence

2. Footprint Evidence • Footprint evidence is typically a shoe print. • Footprints are always left at a crime scene. However, it may be impossible to locate them or differentiate them from other prints. • Usable footprints are found at approximately 40% of crime scenes.

3. Footprint Evidence • The first recorded forensic use of footprints was Warwick, England in 1816. • A young maidservant had been drowned in a shallow pool of water. • While investigating the damp ground around the pool, police discovered footprints and an impression of corduroy cloth with a patch sewn on it.

4. Footprint Evidence • Bits of grain were found surrounding the footprints. • When police searched a nearby farm, they found that a laborer’s pants matched the patch, his footprint was the same size, and the wheat he was threshing matched the grains at the crime scene.

5. Footprint Evidence Characteristics • Class characteristics are not unique, however they can narrow the pool of possible shoes: • Size • Style • Tread pattern • Individual characteristics such as cuts, cracks, embedded objects, and wear patterns help to identify a specific shoe.

6. Individual Characteristics • Most wear occurs at the front and rear of a shoe. • A person with neutral pronation (arch flattening) will have even wear on the front and rear.

7. Individual Characteristics • A wear pattern on the inside of the shoe indicates a person who walks with overpronation. • The ankle is turned in, toward the other foot.

8. Individual Characteristics • A wear pattern on the outside of the shoe indicates a person who walks with under pronation or supination. • The ankle is turned out, away from the other foot.

9. Footprint Evidence • Possible information in print / impression evidence: • Size, type, and model of shoe • Wear patterns and individual characteristics • Sex, height, and weight of the wearer • If the person was carrying a heavy object or running • Number of suspects • Path taken through the scene • Entry and exit points • Linking multiple crime scenes • Association with vehicle tire treads

10. Footprint Evidence • There are no standards for the number of individual characteristics needed to match a shoe to a print. The characteristics selected must be obviously unique to present a compelling argument in court. • Smaller footprints that are slightly pigeon-toed (pointing inward) likely belong to a woman. Men tend to walk with their toes straight or outward.

11. Footprint Evidence • Deep footprints with the front pressed deeper than the rest of the print and a long stride indicate running. • The depth of a footprint may give information about the weight of the person wearing the shoe. • If the prints are consistently deeper on one side, the person was likely carrying something.

12. Footprint Evidence • The height of the wearer may be roughly estimated by measuring the stride length and shoe size. • Foot length is about 15% of a person’s height.

13. 3 Categories of Footprint Evidence • Visible two dimensional print • Material picked up by shoe and deposited onto flat surface. • Recovery is complex due to the variety of surfaces and materials deposited (dust, residue, soil, blood, petroleum products, etc.) • Latent two dimensional print • Dirty shoe on clean floor (dust) • Clean shoe on dirty floor (dust, wax/polish) • Three dimensional impression • Found in soft dirt, sand, mud, or snow • Requires making a cast of the print

14. 2d Prints • Positive Impressions result when a shoe sole accumulates and then deposits material that is transferred in the shape of the areas of the sole that actually contact the ground surface. • Negative impressions are produced when the shoe sole removes residue (dust, blood) from a surface, leaving the residue where the areas of the sole did not come in contact with the substrate.

15. Recovery of Footprint Evidence • Crime scene access is controlled to reduce potential damage to latent prints. • All footprints should be well documented by photographs. • Some latent prints can be visualized by darkening a room and using a bright light at a low angle. • When photography is complete, objects containing footprints should be removed if possible (paper, glass) for further analysis.

16. Recovery of Footprint Evidence • A thorough search of the scene would include examinations of: • flooring at the scene. • pieces of paper or broken glass on the floor. • doors or walls that may have been kicked. • raised surfaces that may have been walked on such as chairs, counters, desks, etc. • outdoor areas near points of entrance or exit from the scene.

17. Enhancing Footprints • Many chemical methods exist for treating a footprint for detection or enhancement. • Reagents for this purpose include: • Leuco Crystal Violet • Amido Black 10B • Diaminobenzidine • Luminol • Fuchsin acid • Patent Blue V

18. Footprint Lifting • Lifting improves the visibility and detail of the impression by transferring it to a surface that provides better contrast. • Electrostatic dust print lifting devices charge a plastic film which is placed over a dust print. This causes the dust to adhere to the film. • The print must be composed of loose dry residue for this method.

19. Footprint Lifting • Depending upon the surface and location the print was left, forensic investigators may have a narrow window in which to lift the print. • Prints left in blood may last for years, whereas prints left in water may evaporate, and prints made with sand may be brushed away.

20. Footprint Lifting • Latent prints may be dusted with fingerprint powder and lifted with gelatin lifters. • These lifters have a thick layer of gelatin on a vinyl or cloth backing that is covered with a protective clear cover sheet. They can lift impressions from any surface, porous or nonporous.

21. Collecting Impressions • Impressions are three dimensional. To preserve them and bring out detail for analysis, a casting is made. • A description of the impressions, their position and direction, substrate, and weather conditions should be recorded before casting.

22. Collecting Impressions • General scene photographs are taken in series from long to middle to close distances to document the relationship of the impressions to the scene. • For impressions in snow, Snow Print wax or an aerosol paint can be lightly sprayed at an angle, from 50-60 cm away, to highlight the ridges or high spots of the impression. This will add contrast.

23. Collecting Impressions • Prints left in the rain may be full of water. A pipette can remove the excess water. • A hair dryer will dry the print enough for the casting material to cure. • A frame is always placed around footprint evidence before casting to make a studier casting.

24. Collecting Impressions • Dental stone is usually used to make a casting. This is a gypsum-based product (like drywall) that has been modified for use in the dental industry. It has minimal shrinkage when cured and captures minute details. • Before casting, fixatives such as dust hardeners are sprayed into the impression to stabilize it during the casting pour.

25. Obtaining Standards • Impressions, lifts, and photographs of found prints are all unknowns. • Standards are needed to give the evidence context. • Without standards, there can be no match.

26. Obtaining Standards • Standards are taken from first responder footwear to eliminate their prints from the evidence. • Additional samples may be taken from the suspect, victim, and witnesses.

27. Obtaining Standards • Standards can be obtained in several ways: • Photography • Adhesive lifters • Inkless prints • Foam impressions • Actual footwear

28. Footprint Databases • The United States does not currently have a national database exclusively for footprints, however, research funded by the U.S. Department of Justice is currently being completed. • Computer scientists are developing algorithms for matching shoe prints. They are hoping to automate the process to make it a query search similar to that of Google search.

29. Footprint Databases • There are also two commercial databases that help identify the types of shoes found at a crime scene. • Treadmarkuses four parameters to help identify outside sole impressions to ease time-consuming recovery. • Solemateis a database holding manufacturer information and several pictorial images to help determine the type of shoe the print belongs to. This database has over 12,000 different shoes including work, sports, and casual shoes.