Anatomy of an Accident

Article excerpt

In much the same way as a medical examiner tries to understand how a person died, forensic engineers are often summoned to the scene of a disaster to scrutinize rubble and debris to determine what went wrong. Learning why an incident occurred, or what factors influenced the amount of damage, can be critical in preventing future incidents or defending expensive litigation. Forensic engineering enables companies and risk managers to isolate the roles of factors such as engineering design, operator error, environmental influences and component failures in accidents and near-misses.

Findings from forensic analyses can help form the basis for failure prevention and risk management strategies. Practical recommendations can be developed to address any root causes identified by the investigation. Future risks can be decreased either by eliminating causal factors or mitigating effects of an incident.

LAUNCHING AN INVESTIGATION

The nature and complexity of the incident, and the technical issues involved, help determine the appropriate size and composition of a forensic investigation. The core of the forensic team can be drawn from the company's in-house staff, vendors or consultants. Appropriate technical, safety, regulatory or legal specialists can also be important contributors. Team members should examine each technical aspect of the incident, such as relevant engineering designs, testing and simulation results and past operations performance. Often, industry norms and trends are examined to obtain insight into specific incidents.

A forensic investigation usually begins with an inspection of a product involved in an incident and the incident site to collect and preserve as much evidence as possible. To facilitate this review, the site should remain undisturbed for as long as practicable. Except for safety reasons, nothing should be moved before adequate documentation, measurement, photography or video taping is completed. A simple inspection may involve preparing a few photographs or measurements, videos or even simple sketches and notes. In more involved cases, computerized equipment and drawings are employed to accurately survey a site or a product.

During the survey, investigators create and maintain an inventory of all evidence, which may include damaged and undamaged parts as well as samples of fluids, lubricants, soils, debris, gases, residues or surface deposits. Lighting conditions and vision obstructions, such as congested equipment, obscured signals, buildings or foliage, are noted. All damage to an affected object or distortion of structural elements is surveyed.

For example, in an investigation of an explosion at an industrial facility, a damaged lightbulb in an adjacent room gave investigators a clue about how far the walls had deflected out during the explosion. This then allowed them to estimate the explosion's size and location.

Environmental evidence, such as visual and photographic records, are examined to help reconstruct accident site features. Photogrammetric techniques that use photographs to determine measurements can help investigators locate key items of evidence that appear in scene photos taken at the time of the accident but that no longer exist at the site. In some cases, it may be necessary to locate and reconstruct important items of evidence, such as tire marks from a vehicle accident.

Physical evidence examination can be performed using nondestructive or destructive methods. Nondestructive methods include visual examination, X-rays and thermal imaging. Destructive methods include sample sectioning to expose internal structures or chemical, bum or stress tests of materials. These methods attempt to uncover physical causes of the accident. Typical problems identified by these methods may include overload fracture, distortion, fatigue, instability, wear from erosion and environmental effects. Visual examinations can also identify evidence of high-temperature effects, such as burning, melting or surface deposits. …