Forensic Biomechanics

Question 1

Forensic Biomechanics

Answer 1

• Application of biomechanics to justice system
• Involves criminal and civil cases
• includes toxicology, pathology, chemistry, computers, accounting and biomechanics
• Use biomechanics has helped identify criminals

Question 2

Types of Footprints

Answer 2

• Impressions: foot sinks into surface
• Tracked Substances: Mud, water, paint, blood

Question 3

Key identifiers from footprints

Answer 3

• Height: Correlated with foot length/width (±10 cm error). Stride length may help but depends on velocity.
• Weight: Depth of impression indicates force (subject may carry extra weight).
• Velocity: Walking leaves full prints; running shows forefoot- only prints.
• Shoe Type: Tread pattern identifies manufacturer and model.
• Foot Structure: Barefoot prints reveal arch type; tread wear patterns may link to a suspect.

Question 4

Forensic Gait Analysis

Answer 4

• People can recognize others by their unique walking patterns
• Assessment and evaluation of a suspect’s gait
• Compare gait features with crime scene evidence
• Used for criminal and personal identification
• Not yet capable of true identification . Therefore, gait is used as supportive evidence

Question 5

First use of forensic gait analysis

Answer 5

• Firth presented in court over 175 years ago.
• A burglar in England was convicted using video surveillance gait analysis. Surveillance footage showed bowed legs and an unusual left arm movement.
• The suspect’s gait was recorded in custody.
• A biomechanist matched the two walking patterns, confirming identity, even with masked face.
• Comparison, not direct recognition
• Observer-based analysis evaluates specific gait features from footage

Question 6

Denmark Bank Robbery

Answer 6

• Case: Bank robbery in Denmark captured by two video cameras.
• Frame rate: 5 frames per second—too low for dynamic gait analysis.
  Postural features were analyzed instead.
• Two camera angles: Frontal view & sagittal view allowed for 3D photogrammetry.
• Key findings: Height, eye level, and shoulder height of the robber and suspect matched within 3 cm.

Question 7

What does reliability in gait analysis depend on

Answer 7

• Analysis method
• Subject characteristics
• Observer experience

Question 8

Factors influencing gait analysis

Answer 8

INTERNAL
- Gender, age, walking speed, injuries, disorders, emotions, body weight, pregnancy, substance impairment
EXTERNAL
- walking surface, type of clothing and footwear, carrying an object, elapsed time

Question 9

Forensic Science in Reality

Answer 9

• Most cases do not involve homicide; forensic work spans various crimes
• Lab tests take months, not minutes, and reenactments are rare
• DNA testing is backlogged; even rush results take days

Question 10

Challenges in court with forensic biomechanics

Answer 10

• Juries expect absolute proof but must rely on expert opinions (e.g., “likely” or “possible”).
• Defense concerns: Juries may see forensic experts as infallible.
• Computer simulations are widely used due to cost and time constraints of full lab reenactments

Question 11

TV Misrepresentation of forensic biomechanics

Answer 11

• Over-the-top techniques (e.g., perfect knife cast from a wound) are unrealistic.
• Real forensic work involves careful dissection, scanning, and analysis

Question 12

Factors contributing to falls

Answer 12

• Environmental: Slippery floors, uneven surfaces, poor lighting
• Physical Health: Balance issues, muscle weakness, reaction time
• Behavioral: Footwear, distractions, sudden movements

Question 13

Key biomechanics components of falls

Answer 13

1. Initial Contact:
   * Balance loss shifts center of mass
   * Example: Forward falls → outstretched arms → wrist fractures
2. Energy Transfer:
   * Impact force depends on surface hardness
   * Example: Concrete → high force, severe injuries
3. Injury Mechanisms:
   * Vertical falls (heights) → spinal & lower limb injuries
   * Lateral falls → hip & shoulder fractures

Question 14

Falling investigation techniques

Answer 14

1. Reconstruction Models
   * Uses computer simulations & physical models to recreate the fall.
   * Analyzes pre-fall movements, fall dynamics, & body impact.
   * Helps identify cause & potential contributing factors.
2. Injury Analysis
   * Examines injury patterns to assess fall severity & mechanics.
   * Compares injuries with known biomechanical thresholds.
   * Determines if injuries are accidental or suggest foul play.
3. Environmental Factors
   * Evaluates lighting, surface texture, obstacles.
   * Identifies slip/trip hazards to establish liability.
   * Important in workplace & public space investigations.

Question 15

Numerical simulation

Answer 15

Enables an objective and quantitative analysis of human kinematics and body loading

Question 16

Case study with numerical simulation

Answer 16

• Investigators were unsure if a victim
  found on the pavement was murdered,
  accidentally fell or committed suicide.
• Some injuries were typical of a fall, but
  others were unassigned such as blood
  stains 2.2 meters away from the body.
• Skin laceration in occiput region,
  posterior skull fracture, superficial
  injury to lumber spine due to skin
  stretching, teeth knocked out, aorta
  partially torn, fracture to upper
  sternum, all ribs cracked, and
  compressive fractures to two thoracic
  vertebral bodies.
• Simulations tested different fall scenarios
• Injury severity and landing distance suggest a fall from the highest balcony
• A push or throw from a lower height could result in the same landing distance but with less severe injuries
• If pushed from the highest balcony the landing distance would be too great, making this scenario unlikely

Question 17

Summary of analysis on numerical case study

Answer 17

• Numerical simulation confirmed all injuries resulted from a single event.
• No signs of a struggle were found at the scene.
• No defensive injuries on the upper extremities, suggesting no act of violence.
• Toxicology reports negative, ruling out impaired consciousness.
• Expert opinion indicated suicidal behavior as the likely cause.
• Police investigation later revealed personal struggles, and a past suicide attempt as potential motives.

Question 18

Qualifications to be an expert witness

Answer 18

• Must have expertise through education, training, skills, or experience
• Bachelor’s degree and specialization in biomechanics meets the minimum qualification

Question 19

Role of a biomechanist in legal cases

Answer 19

• Involved in criminal cases (e.g., assault, murder).
• Involved in civil cases (e.g., personal injury, negligence, insurance fraud).
• Provides an expert opinion on the strength of the arguments based on physics, anatomy, physiology, and
  mechanics.

Question 20

Steps in forensic analysis

Answer 20

1. Review Documentation
   * Examine witness statements, medical records, and expert reports.
   * Accept medical conclusions (not qualified to interpret medical test results) unless errors are suspected, then inform legal teams.
2. Search Scientific Literature
   * Find relevant scientific literature on tissue tolerance, stress/strain limits, and biomechanics principles.
3. Conduct Biomechanical Analysis
   * Synthesize information, use mock testing, mathematical models, simulations, statistics, and field testing.
4. Write the Expert Report
   * Address both legal arguments and provide a conclusion.
   * Use terms like “likely,” “unlikely,” “highly likely,” or “possibly” to express scientific certainty.