My favorite doctrine from law school may have been Res ipsa loquitur -- "the thing speaks for itself."
So much elegance, simplicity & common sense in this legal doctrine!
Normally, if you are harmed by someone, YOU have the burden to prove that they harmed you. This is why, in cases you hear about in the news (like a high profile murder case), the prosecutor has to prove to the jury that the defendant(s) committed the alleged crime.
But, sometimes, the facts of a case are so unusual that it makes sense to flip the burden of proof onto the defendant -- to prove that they DIDN'T do the crime they're accused of.
For example, if you live in a residential neighborhood that has just one business in it - a bakery - and, one day, during your evening walk, a barrel of flour falls onto your head -- then, it would be silly to require you to prove that the bakery is responsible. Because, who else would have a barrel of flour sitting around? (Here, it makes more sense to assume that the bakery is responsible, unless they can prove otherwise.)
Those, in fact, were the exact facts of the case that gave rise to the doctrine of Res ipsa loquitur! In 1863, poor Mr. Byrne was struck in the head, during his evening walk, by a falling barrel of flour; right underneath a bakery window.
As the judges wrote in their decision, "A barrel could not roll out of a warehouse without some negligence... and if there is any state of facts to rebut the presumption of negligence, [the bakery] must prove them."
Sometimes, the thing speaks for itself!