Journal of the National Academy of Forensic Engineers

Forensic Engineering Application of the Matchmoving Process

Richard M. Ziernicki — 2018-01-01

This paper presents a methodology that uses the photogrammetric process of matchmoving for analyzing objects (vehicles, pedestrians, etc.) visible in video captured by moving cameras. Matchmoving is an established scientific process that is used to calibrate a virtual camera to “match” the movement and optic properties of the real-world camera that captured the video. High-definition 3D laser scanning technology makes it possible to accurately perform the matchmoving process and evaluate the results. Once a virtual camera is accurately calibrated, moving objects visible in the video can be tracked or matched to determine their position, orientation, path, speed, and acceleration. Specific applications of the matchmoving methodology are presented and discussed in this paper and include analysis performed on video footage from a metro bus on-board camera, police officer body-worn camera footage, and race track video footage captured by a drone. In all cases, the matchmoving process yielded highly accurate camera calibrations and allowed forensic investigators to accurately determine and evaluate the dynamics of moving objects depicted in the video.

Forensic Engineering Investigation of a Fatal Farm Tractor Incident

Daniel P. Couture — 2018-01-01

A farm owner was found unresponsive with crushing head injuries on his property in rural Ontario. His small farm tractor was found 60 meters away down a small incline with the engine running and transmission in neutral. The owner’s son alleged that when the parking brake was engaged (with the engine running and transmission in neutral), this tractor’s parking brake would “pop out,” allowing the tractor to move. Field tests were conducted on the tractor to attempt to duplicate the scenario and to determine if the alleged sequence of events was plausible. Components of the parking brake and one exemplar were assessed with specialized metrology to determine whether they were within the manufacturing specifications on the blueprint. A 3-D CAD model of fit was created, and several variances were identified between the parts and the factory drawing. The results of the analysis concurred with the scenario that these variances led to the disengagement of the parking brake and operator fatality.

Engineering Analysis of Cost to Protect Workers from Diacetyl Exposure and the Economic Benefit of Noncompliance

Drew Peake — 2018-01-01

Large commercial bakeries use artificial butter flavor (containing diacetyl) in its recipes, and have for more than 40 years. In 2012, a health-based exposure threshold was published for diacetyl by the American Conference of Governmental Industrial Hygienists (ACGIH). Bakery managers typically knew what was necessary to protect workers from exposure. However, for a variety of reasons, most did little to control exposure: The Food and Drug Administration said diacetyl was generally recognized as safe; substitute products had not been demonstrated as less harmful; and no regulatory standard had been established. This study develops the costs that would have been necessary to protect workers, using the U.S. EPA model (known as BEN) to calculate the economic benefit of noncompliance, and offers a characterization of the profit incentive to place workers at risk.

Forensic Engineering Analysis of Fire Caused by Control Failure Due to Deviation from Patented Design

John Certuse — 2018-01-01

A fire in a multi-unit condominium complex occurred, causing the building to be a complete loss. The point of the fire’s origin was traced to a recently drained hot tub’s electric heater. Examination of an exemplar heater revealed that a key safety-related control feature was manufactured in a configuration inconsistent with its original patent drawings in a way that would have lessened its performance for what may have been cost of manufacturing considerations. This change also brought into question whether the control that was reportedly tested at Underwriters Laboratory was one designed to the patent specifications. The manufacturer has since discontinued use of the control for subsequent installations.

Forensic Engineering Analysis of Commercial Vehicle Air Brake Systems Performance

Jerry S. Ogden — 2018-01-01

Braking systems for heavy commercial vehicles differ greatly from the design for light-duty motor vehicles. For example, 49 CFR 571.121 and 49 CFR 393.52 require loaded buses, single unit commercial vehicles, and vehicle-trailer combinations equipped with air brake systems to generate sufficient braking force to meet specific stopping distance, stopping acceleration rate, and brake force-to-weight percentage performance criteria. The combination of unique design, mechanical complexity, and maintenance issues characteristic to air brake systems also pose difficulty in the analysis of air brake system performance. Air brake system performance presents a difficult problem for the forensic engineer with limited familiarity regarding air brake system functions and the elements affecting brake performance. This paper provides insight into the evolution of air brake system standards and the applicable performance criteria for heavy commercial vehicles. The methods presented allow the forensic engineer to mathematically analyze and determine the effects of brake size, mismatched components, brake adjustment, and system air pressure on the overall braking force and stopping capabilities of air brake equipped commercial vehicles.