Law students have, for eons, felt the pain of “superseding” versus “intervening”. Professors throw these terms around as if they are household words. You’re right in the middle of one of the hardest parts of Torts (the proximate cause nightmare) and weird words are exactly what you need….
Then, to make matters worse, professors who are trying to be cute like to coin their own expressions like “Superseding-intervening”… or even better, some pretend that they’ve never heard of the terms at all. Yeah, good one. Act like you’re not planning your lesson by reading Emmanuels and E&E the night before.
So here’s our chance to make it simpler. The real question that you’re wondering about is “what kinds of events break the chain of causation to an original negligent defendant and what kinds of events do not break that chain?”.
Quick definition: Intervening = we expected this. Superseding = we did NOT expect this.
Allow me a brief example:
You get into a car accident. It’s the other guy’s fault, because he was driving like a jackass. The EMTs arrive on the scene and they screw something up, which is pretty much what we expect, because if the EMTs weren’t jackasses, they wouldn’t be EMTs. Then, you get to the hospital and the doctor screws something up, because the doctor was a busy jackassing around instead of listening to you. You’ve had some pretty bad luck, but none of it is really that strange.
Contrast that situation to this one:
Same car accident. Still the other jackass driver’s fault. Only this time, the EMT turns out to be Batman, and he hits you in the neck with one of those Bat-Boomerangs. That’s way more than bad luck.
See? We expect people to be jackasses. We do not expect them to be Batman.
If the chain-of-events kind of thing that happens is something we expect (like several people acting like jackasses), then we dub it an “intervening cause”… which means “yeah, this happened, and it sucks, but the original defendant is still on the hook for the negligence because it was something we all knew could easily happen.”
On the other hand, if that chain-of-events thing is something really out of the ordinary (like Batman), then we dub it a “superseding cause”… which means “Really? We would never really have expected that, so the original defendant is only responsible for the damage he directly caused, but not this new damage.”
Mnemonic? Superseding… Superhero…. Batman.