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Gait forensic science


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Not really my own. Picked from Slideshare. Added few of my own slides though.

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Gait forensic science

  2. 2. Definition  Locomotion or gait –  Gait is the medical term to describe human locomotion or the way that we walk.  Thus, it is a locomotion achieved through the movement of limbs.  Different gait patterns are characterized by differences in limb movement patterns. Thus, every individual has a unique gait pattern, while there are some features in a person’s gait that are common for everyone.  There are many types of gait such walking, crawling, jogging, running and skipping. 2
  3. 3. GAIT ANALYSIS AND RECOGNITION  Under forensic science, gait is studied through forensic gait analysis which includes the identification of gait features and patterns of subjects seen on CCTV and from footprints forming a gait pattern left at the scene of a crime.  The height of an individual can be determined by his/her footprint and shoe print, as the foot tends to be approximately 15 % of the person’s average height.  Footprints are left at the scene of a crime forming a recognizable gait cycle.  The most studied gait features since 1970s is the lower limb, as the leg motion can be effectively used as a cue to identify a person.  Gait recognition techniques :  Automatic analysis of Video Imagery  Radar System 3
  4. 4. Gait IDENTIFICATION  Gait pattern is identified from the  Direction line,  Walk line,  Foot line,  Foot angle,  Step angle,  Step length,  Step time,  Stride length,  Stance and Swing phase,  Cadence,  Velocity,  Width of the steps;  and other special features of the foot or footwear, in addition to usual wear and tear of the footwear (numerous creases, flatfoot character, horizontal & vertical ridges, corns, deformities.) 4
  5. 5. Gait CYCLE  Gait cycle is used to describe the complex activity of walking, by describing the motions from the period of time from one heel strike on the ground to the next strike of the same heel, on the ground for a second time.  PHASES OF GAIT – Gait cycle is divided into two phases :  Stance : Defined as the interval in which the foot is on the ground (60 % of the gait cycle.)  Swing : Defined as the interval in which the foot is not in contact with the ground (40% of the gait cycle.) 5
  6. 6. Stance phase  It begins at the instant that one extremity contacts the ground & continuous only as long as some portion of the foot is in contact with the ground.  It is approx 60% of normal gait duration. 6
  7. 7. Swing phase  It begins as soon as the toe of one extremity leaves the ground & ceases just before heel strike or contact of the same extremity.  It makes up 40% of normal gait cycle. 7
  8. 8. Double support  It is the period of time when both feet are in contact with the ground.  This occurs twice in the gait cycle – at the beginning and end of stance phase – and also is referred to as initial and terminal double limb stance.  It accounts to approximately 25% of gait cycle.  This phase is absent in running 8 SINGLE support  It is the period of time when only one foot is in contact with the ground. In walking, this is equal to the swing phase of the other limb.
  9. 9. Subdivision of phases Stance phase – 1) Heel strike (Initial Contact) 2) Foot flat (Loading Response) 3) Mid-stance (Mid Stance) 4) Heel off (Terminal Stance) 5) Toe off (Pre Swing) Swing phase – 1) Acceleration (Initial Swing) 2) Mid-swing 3) Deceleration (Terminal Swing) 9
  10. 10. subDivision of Stance phase 10
  11. 11. Subdivision of Swing phase 11
  12. 12. REPRESENTATION OF COMPLETE Gait cycle 12
  13. 13. PECULIAR FEATURES  It is sometimes required to determine whether a person was walking, running or standing.  A running man exerts about 2-3 times the pressure he exert in his walk, therefore, the shapes and sizes of the marks and the step length vary.  Step length in a slow walk is about 60 cms while it increases to about 90 cms in running.  It also varies from man to man according to his height and habits.  A standing man gives clear mark of his foot or footwear – There are drag or slippage marks if he is walking or running.  If an individual has stood for sometime at a particular place, the marks at the spot are found somewhat damaged. 13
  14. 14. factors affecting variables  Age,  Gender,  Height,  Size & shape of bony components,  Distribution of mass in body segments,  Joint mobility,  Muscle strength,  Type of clothing & footwear,  Habit,  Psychological status. 14
  15. 15. Saunders’ Determinants of gait  Gait “determinants” was first described by “Saunders & Coworkers” in 1953.  The “determinants” represent adjustments made by the pelvis, hips, knees, foot and ankles affect energy expenditure and the mechanical efficiency of walking. 15
  16. 16. GAIT ABNORMALITY  It is a deviation from normal walking.  There are numerous causes of abnormal gait.  There can be great variation depending upon the severity of the problem.  If a muscle is weak, how weak is it?  If joint motion is limited, how limited is it? 16
  17. 17. VALUE OF GAIT EVIDENCE  If a crime had happened in a village where there were no CCTV cameras or anything, gait evidence can be used by taking cue from the footprints left at the crime scene.  Any conviction cannot be given on the basis of gait alone; it has to be corroborated by other evidences. 19
  18. 18. PRITAM SINGH and Anr. V. STATE OF PUNJAB AIR 1956 SC 415  Case of murder; accused fled away; tracks found; identity of one established by looking at his gait pattern.  Accused made to walk with four other men for the identification of foot prints.  Accused walked with a distinct limp; very much less marked on previous occasions.  The evidence of the trackers sufficiently established that one of the culprits made footprints which showed that his way of walking was outwards and he put his right foot more outwards than the left.  Thus, the limp in the gait had created impressions which were particularly characteristic of this accused and went onto corroborating the story of prosecution that the tracks obtained from crime spot was of the accused.  This was also demonstrated by the impressions which the accused made when he walked in the District Jail with the shoes given to him there on the sandy patch, which was specially prepare for that purpose.  His identify was thus established as the culprit, using the track evidence. 18
  19. 19. Reference  Sharma, B.R., ‘Forensic Science in Criminal Investigation and Trials.’ 4th Ed, Universal Law Publishing, New Delhi.  Vij, Krishan., ‘Textbook of Forensic Medicine & Toxicology.’ 4th Ed. Elsevier Publications.  Modi., ‘Medical Jurisprudence & Toxicology.’ Lexis Nexis, Buttersworth (2010)    analysis   19
  20. 20. THANK YOU !! 20