Forensic Physics: Gait Analysis from CCTV and Biomechanics

This mock test covers forensic gait analysis, a discipline within forensic physics that uses biomechanical measurement and CCTV footage to establish the identity or physical characteristics of unknown individuals captured on surveillance cameras. Topics span the complete gait cycle (stride length, step length, cadence, foot progression angle, walking speed), the 60/40 stance-to-swing ratio, double-support intervals, and the six determinants of gait (Saunders, Inman and Eberhart). Pathological gait patterns -- antalgic, Trendelenburg, hemiplegic (circumduction), foot-drop (steppage), and Parkinsonian (festination, shuffling) -- are tested with distractor sets that differ on the single biomechanical parameter separating each disorder. CCTV methodology including camera angle optimisation for specific parameters, frame-rate limitations on temporal measurements, barrel-distortion correction, and photogrammetric height estimation from reference objects is covered at examination depth. Landmark casework includes the Birmingham 7 case and R v Otway [2011] EWCA Crim 3 (UK) and the application of the US Daubert standard to gait methodology.

For Indian forensic science aspirants, this mock is relevant because AIIMS Delhi has an active biomechanics laboratory contributing to clinical and medicolegal gait research, and CFSL Chandigarh has applied gait-related biomechanical analysis in accident reconstruction casework. Indian courts have not yet generated specific reported gait identification judgements; admissibility would be evaluated under Section 45 of the Indian Evidence Act 1872 (now Section 39, Bharatiya Sakshya Adhiniyam 2023) as expert opinion on a matter of science. This is an emerging area for UGC-NET candidates, NFSU MSc Forensic Physics aspirants, and forensic science professionals entering CFSL or SFSL roles.

Topics covered:

• Gait cycle parameters: stride length, step length, cadence, foot angle, walking speed
• Stance phase (60%%), swing phase (40%%), and double-support intervals
• Pathological gait: antalgic, Trendelenburg, hemiplegic, foot-drop, Parkinsonian
• Biomechanics: inverted pendulum model, CoM oscillation, six determinants of gait
• Soft-tissue artifact in 2D and 3D motion capture
• CCTV gait analysis: camera angle, frame rate, lens distortion correction
• Photogrammetric height and distance estimation from reference objects
• Appearance-based (GEI) vs model-based gait recognition; casework admissibility

Allow 30 minutes.