Judson B. Welcher

Executive Vice President
Accident Reconstruction, Biomechanics

Dr. Judson Welcher is a Biomechanical Engineer and Accident Reconstructionist with Aperture (formerly Biomechanical Research and Testing). Judson has been employed in the field of biomechanical engineering and accident reconstruction for over 28 years. He specializes in trauma causation and prevention, human tolerance, restraint design, instrumented testing with humans and anthropomorphic test devices), accident reconstruction, and amusement park rider tolerances. Judson has consulted on thousands of civil and criminal forensic cases; he has testified in local, state, and federal courts regarding accident reconstruction and biomechanical engineering across the country. Judson has qualified and testified as an expert in over 200 trials. 

Judson holds a Bachelor of Science in Mechanical Engineering from California Polytechnic University, San Luis Obispo and a Master of Science in Biomedical Engineering from the University of Southern California. His dissertation research focused on developing and testing a new sensor for quantifying the loads within the human lumbar spine under various conditions and his master’s thesis was titled “Whiplash Associated Disorders: Related Anatomy, Biomechanics of Injury, and the Relationship Between Injury Potential and Automotive Seat Design.”

Judson has been accredited through the Accreditation Commission for Traffic Accident Reconstructionists (ACTAR) since 1995 and during that time has performed and analyzed over 1,000 staged instrumented human volunteer crash tests and authored over 45 technical publications and presentations on collision trauma biomechanics, injury causation, human tolerance, automotive seat design, head restraint design, and accident reconstruction. He has taught classes in the areas of accident reconstruction and biomechanical engineering for Texas A&M Engineering Extension Services (TEEX), the Collision Safety Institute (CSI), and the Riverside Clark Training Center for Law Enforcement & Public Safety Training. Due to his extensive experience, Judson has been invited to speak to audiences of engineers, accident reconstructionists, law enforcement personnel, physicians, and attorneys at various conferences and seminars. Notably, many aspects of his research have been featured on television shows like 60 Minutes, Nightline, Discovery Channel, and various news channels across the country.

Judson is a member of the American Society of Biomechanics (ASB), American Society of Mechanical Engineers (ASME), Association for the Advancement of Automotive Medicine (AAAM), Biomedical Engineering Society (BMES), Pi Tau Sigma Mechanical Engineering Honor Society, Society of Automotive Engineers (SAE), and Southwestern Association of Technical Accident Investigators (SATAI). He is also a member of the ASTM International - F24 Committee on Amusement Rides and Devices.

Judson B.'s Expertise

  • Accident Reconstruction
  • Biomechanical Analysis
  • Vehicle Inspection
  • Crash Data Retrieval


Ph.D. Biomedical Engineering

M.S. Biomedical Engineering

B.S. Mechanical Engineering

Professional Certifications


Crash Data Retrieval Technician

Work Experience

Aperture, LLC (formerly Biomechanical Research & Testing, LLC) Long Beach, CA, October 1994 - Present, Biomechanical Engineer and Accident Reconstructionist / Principal

  • Responsible for the analysis of injury-causing accidents and accident reconstruction.  This includes vehicle inspections, accident reconstruction and necessary biomechanical engineering calculations. Performs biomechanical testing to determine occupant response to various types of accidents and forces. Conducts fully instrumented tests in which human subjects are used (has conducted over 1000 instrumented vehicle impact tests). Data collected includes acceleration, high speed film/video, and electromyography (EMG). Has evaluated bumper, restraint system and seat design/response to impact. Conducts ongoing research to evaluate human tolerance and injury mechanisms associated with accidents. Performs biomechanical analyses of various events for purposes of litigation, including impact reconstruction and occupant force exposure and injury potential.
  • Provides forensic consultation for amusement park incidents involving the evaluation of occupant force exposure and injury potential. Consults with theme park developers and amusement park operators to test and determine vehicular and biodynamic response of various rides and attractions. Conducts fully instrumented human subject testing of amusement park attractions.  Has tested roller coasters, motion platforms, water rides, go-kart/bumper cars, and video arcade attractions for purposes of ride evaluation, design and development. Currently serves on the ASTM F-24 committee to develop biodynamic standards for testing and evaluation of amusement rides. 

Clark Training Center, Law Enforcement & Public Safety Training, June 2009 & January 2010, Instructor – Traffic Collision Investigation (TCI) – Reconstruction (POST certified)

  • Teach a half day course on an “Introduction to Biomechanics – Occupant Kinematics and Collision Trauma Biomechanics (injury).”  Topic covered include: Definitions of Occupant Kinematics and Biomechanics, Occupant Protection Systems, Occupant Kinematics in Frontal, Rear, Side (near and far), Rollovers and Other Crashes, Occupant Simulation Models for Occupant Kinematics, and Sources of Information and References. 

Texas A&M University, Texas Engineering Extension Service, College Station, TX, 1996 - December 2001, Assistant Adjunct Professor / Instructor

  • Taught (beginning in 1999) “Collision Trauma Biomechanics” courses periodically through the year.  Taught "Analysis of Low-Speed Collisions" courses periodically through the year.

Biodynamics Engineering, Inc., Pacific Palisades, CA, September 1990 - October 1994, Biomechanical Engineer 

  • Responsible for the biomechanical analysis of injury-causing accidents. This included evaluation of accident reports, witness statements and medical records, as well as vehicle inspections, accident reconstruction and engineering calculations. Performed biomechanical testing and research to determine human response to various events.

Baxter Healthcare Corporation Edwards Division, Irvine, CA,  June 1989 - September 1989, Associate Engineer

  • Responsible for a root-cause analysis of product failure in an 8F Cardiac Monitoring Catheter. This involved a thorough examination of all the steps of the manufacturing process, with special emphasis on biological compatibility, material selection and processing time. Supervised the inspection of raw fiber optic cables, including training in light dispersion analysis. Constructed and qualified a test fixture for a Right Heart Ejection Fraction Catheter.


Society of Automotive Engineers (SAE)

California Association of Accident Reconstruction Specialists (CAARS)

Southwestern Association of Technical Accident Investigators (SATAI)


CDR/EDR Downloads

3D Laser Scanning

Crash Simulation

Crash Testing

Judson B.'s Expertise

  • Accident Reconstruction
  • Biomechanical Analysis
  • Vehicle Inspection
  • Crash Data Retrieval

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