Overview

CSI for buildings. When a bridge collapses, a car crashes, or a phone battery explodes, Forensic Engineers are called in to figure out why. They work backwards from the disaster to find the truth.

Core Idea

The core idea is The Smoking Gun. Finding the physical evidence that proves what happened.

  • “Was it a design flaw?”
  • “Was it bad maintenance?”
  • “Was it user error?”

Formal Definition

The investigation of failures which may lead to legal activity. Key Process: Reverse Engineering the Accident.

Intuition

  • The Puzzle: You have a pile of twisted metal. You have to put it back together mentally to see how it broke.
  • The Witness: Metal doesn’t lie. If a beam is bent a certain way, it tells you exactly how much force hit it and from what direction.

Examples

  • 9/11 Investigation: Forensic engineers studied the steel from the Twin Towers to understand how the fire weakened the structure enough to cause a collapse.
  • Hyatt Regency Walkway Collapse: The deadliest structural failure in US history. Engineers found a tiny change in the design of a connection rod that doubled the load on a nut.
  • Samsung Galaxy Note 7: Why were phones exploding? Forensic engineers found that the battery was slightly too big for the case, causing it to pinch and short circuit.

Common Misconceptions

  • It’s just guessing: It involves rigorous testing and computer simulation to prove the theory.
  • They are lawyers: They are engineers who testify in court as “Expert Witnesses.”
  • Standard of Care: Did the original engineer do what a “reasonable” engineer would have done? If not, it’s Negligence.
  • Subrogation: Insurance companies hiring engineers to prove it was someone else’s fault so they can get their money back.

Applications

  • Product Liability: Suing a car company because the airbag didn’t deploy.

Criticism / Limitations

  • Hindsight Bias: It’s easy to see the mistake after the accident. It’s hard to see it before.

Further Reading

  • Petroski, Henry. Design Paradigms: Case Histories of Error and Judgment in Engineering.