Understanding Footprints in Forensics ...........pptx

footprints in forensic science

1. Footwear marks as a forensic evidence Name – SIRAT Class- M.Sc. (1 st year) Roll no. - 23151013

2. Content Introduction Forensic importance Nature Gait pattern Collection of foot impressions Identification techniques References

3. Introduction Footwear marks The marks made by the surface of the sole. That contains distinctive patterns and are believed to be present more frequently than fingerprints. They are found on all types of surfaces.

4. Forensic Importance Presence/absence of culprit/victim Number of persons Tracking the direction of entry or exit Presence of animals Gait Pattern Fig. 2. Footwear Print

5. Nature Footwear Prints Two dimensional. Obtained mainly on hard surfaces (floor, glass etc.) Patent prints (visible prints) Latent prints (invisible prints) Footwear Impressions Also known as plastic prints . Three dimensional. Obtained mainly on pliable surfaces.

6. Gait pattern Gait  is the manner or style of walking. Gait pattern of each individual is unique. It helps to determine: Sex of an individual Height of an individual Age of an individual Fig. 3. Normal walking line Fig. 4. Broken walking line

7. Collection of foot marks There are 4 basic methods for collecting foot marks at the crime scene. These are- Photography Tracing/ sketching Casting Lifting

8. Photography It is the first step for processing the evidence. Camera should be kept parallel to the surface on which the mark is found. The use of 35 mm. camera lens is becoming popular because of the handy size and availability of high quality films for the camera. Fig: photograph of footwear print with scale

9. Sketching/ tracing Crudest but easiest way to record track marks. Glass or plastic sheet is held over the mark. An outline is traced over the sheet and details of the marks. Highly subjective. Not very reliable.

10. Casting Material like plaster of Paris , wax, resins, plastic powders, modelling clay, Sulphur, lead, woods metal, plasticine, moulage material, silicone etc. can be used in the process.

11. Preparation of casts: Removal of extraneous material. Spraying of shellac solution. Spraying of mineral oil. Placing of aluminium frame. Pouring of plaster of Paris. Reinforcing the casts. More plaster of Paris. Allow the caste to settle. Engraving of details of the case. Removing and washing of the casts.

12. Lifting Lifting techniques vary with different surfaces and materials. The following techniques are commonly used: 1. Dust prints By using bromide paper sheet. By using adhesive tape. 2 . Oil prints To lift greasy and sticky prints : dust on the marks with powder and then lifting of the dust prints can be done.

13. Holography : Used for recording prints on carpets (invisible prints), on grass and other surfaces which undergo compression. Compression of fibres take place. The laser beam is able to record this compression on a photographic plate. The photograph obtained is known as hologram. Recent techniques used for lifting prints

14. 2 . Electrostatic lifting technique: Used for lifting invisible marks on floors or floor coverings. Principle: The dust particles can be lifted at high voltage on to a vinyl sheet, where they can be photographed or fixed in a gelatin paper. Process: Black vinyl sheet is taken. Sheet is covered with aluminium foil and high voltage is applied. Photograph is taken of the mark obtained.

15. 3. Silicone casts: These are new plastic compounds. Advantage: They do not adhere strongly to the materials with which they come in contact. Harden quickly in proper conditions. Used to: Lift the prints and shallow impressions from sloping and curved surfaces. Prints even from walls can be lifted.

16. Identification techniques Identification of marks is carried out by comparison of the identifying features present on the suspected marks and the specimen mark prepared Comparison is carried out in following ways: Side by side comparison Super-imposition technique

17. Side by side comparison Comparison of the positions and dimensions of identifying features is done with the help of photographs. Photographs are pasted side by side and a large glass or plastic sheet ruled into small squares is placed over the photographs. The identity or non-identity of the common source becomes apparent at once.

18. 2. Super-imposition technique In this technique footwear is smeared with fingerprint powder and its mark is imprinted on a wide adhesive tape, which in turn is pasted on a transparent plastic sheet. The transparency is ready. It can be placed directly on the questioned mark or its photograph and then can be compared.

19. References Sharma, B.R. (1974). Forensic Science in Criminal Investigation and Trials . Central law Agency. Sharma, B.R. (1980). Footprints, Tracks and Trails In Criminal Investigation And Trials. Central Law Agency. Srihari, S. N. (2011). Analysis of footwear impression evidence.  US DoJ Report . Tang, Y., Srihari, S. N., Kasiviswanathan , H., & Corso, J. J. (2011). Footwear print retrieval system for real crime scene marks. In Computational Forensics: 4th International Workshop, IWCF 2010, Tokyo, Japan, November 11-12, 2010, Revised Selected Papers 4 (pp. 88-100). Springer Berlin Heidelberg.