Finding Proximate Causes are only relative

I noticed today that I had been using the term "proximate cause" in reports for some time and wanted to track down the term a bit. Turns out to have quite a history for expert witnesses all the way back to old English law. Francis Bacon took the time to define it--I won't copy that definition here as his definition was somewhat Shakespearean in use of words.

However, here's the thing. The proximate cause is more or less a legal term used by expert witnesses and lawyers meaning that event which lead, ultimately, to the damage. This is a bit misty though. A fire investigator, as an expert witness, would say the proximate cause was the electric furnace failing. This the event which caused the damage or loss. Fair enough.

Then he calls in an engineer, who will take a different level of viewpoint, which is 'what is the proximate cause for this electric furnace catching fire?' He will dissect and analyze and study and may find that the thermal cut out failed. As an expert witness he may say "Ahah! The failure of the thermal cut-out was the event that lead to the loss." Fair enough.

The insurance company will want to subrogate and ask the furnace manufacturer to cough up some portion of the loss. The furnance manufacturer will naturally want to know why the heck the thermal cut out failed. They may acquire the very component or track back to manufacturing dates and component date codes and find that it was not the only one of that date code that had problems. They will then pursue the component manufacturer, say Fujitsu, and subrogate again.

Fujitsu will be unhappy with all this, of course, and have their own expert witness, forensic engineer, or manufacturing engineer do an analysis on why that component had a problem and they may find that there were chemical impurities in the device.

The chemical impurities were due to some failure on the part of, say, Dupont or Dow Chemical. Again proximate cause is being chased at increasing levels of detail.

Obviously, expert witnesses and forensic engineers tend to want to discuss the mechanical causality--the causal chain--the action and mechanical reaction of a series of concatenated events. One may easily find that the chemical impurities were due to an operator failure: end of the mechanical causal chain. But why did the operator fail? Then you are into the mental and emotional possibilities. His wife was leaving him, his child was found using drugs, etc, which so distracted him that he overlooked or flubbed his duties. (There are psychiatrists posing as 'expert witnesses' who could be consulted--but that's a hole we won't dive into.)

The point? Proximate Cause is NOT an absolute (which are unobtainable). It is only
a relative term for the sphere of operation we are talking about. The house should not have burned down, but it did because the furnace as a component of the house
failed. The furnace should not have started a fire, but it did because of the thermal cutout failure as a component of the furnace. The thermal cutout should not have failed... and so on.

Most expert witnesses understand this intuitively, but I realized it was a missing
element in any definition I could find. I also find that I will chase the causal chain as far as I can, beyond my sphere of operation, whenever possible, but can leave it to stand at the sphere of operation I am working in--for me as an expert witness/forensic engineer: one detail level below the fire scene investigator.

Derek Geer
Forensic Engineer
San Diego, California
www.geers.com