I think of Latin as a sort of garnish to good English. You can't make it the whole meal; nothing smacks of pompous pedantry more than weighing down each sentence with overwrought Latinisms just to show off, or worse, to make it impenetrable to a "lesser mind". On the other hand, there is a certain joy in deploying just the right phrase for maximum effect. Sure, you could make a brilliant argument and just let it speak for itself, but adding Q.E.D at the end is the philosophical equivalent of spiking the football in the endzone. With that, I present some of the more enjoyable fragments I've come across in the last few months. Some are legal technicum that are in wide use, others are merely phrases or peripheral concepts of interest.
In re: You may think that the "re:" in the subject line of an email stands for "regarding". It in fact is the abbreviation of "in re" pronounced "in ray" and means simply "in the matter of". Used in case names when there's no formal adverse parties or the controversy is about the disposition of an item rather than the parties specifically. (ex. "Memo to house, in re: the red thong found on the couch Saturday morning...")
Subpoena duces tecum: This useful little guy is unfairly confined to law courts when it really has broad application to many circumstances. Since a "subpoena" just means means under penalty of punishment, a Subpoena duces tecum is an instruction to "bring it with you under penalty of punishment"...aka "Show up without it and I'll break yo' KNEES". Useful for club treasurers and hosts enforcing BYOB.
Expressio unius est exclusion alterious: The unconscious rule you apply when a braggart is telling you all the mountains he's climbed but only actually names two. "To express one is to exclude others" in law means that if a writing went to the trouble of specifically mentioning something then, by implication, anything not named was deliberately left out.
Ejusdem generis: Unnamed items in a class are assumed of the same type as the named items. It's the unconscious rule that you apply when you see "etc." that suggests that unnamed list items are of the same type as named list items. (Complimentary "soda, water, juice, milk etc." is not gonna get you a free gin and tonic.)
Volenti non fit injuria: The principle that, at least within the legal definition, you can't be harmed by something you consented to. Fight Club and Jackass come to mind.
Res ipsa loquitur: "The thing speaks for itself." Can be used anytime something is self-explanatory. (Original use was in a case wherein a plaintiff was walking in front of a shop and a barrel of flower comes flying out the window and lands on him. The court was tying itself in [Gordian] knots trying to figure out how to fit it into the theory of negligence liability when the judge finally sliced through the morass and declared "res ipsa loquitor: Barrels don't just fall out of the sky. Obviously someone screwed up."
...sed quid in infernos dicet?: "...but what the hell is it saying?" As is often the case,res ipsa loquitor wasn't the tidy solution it was hoped to be. Some wag finally added the pseudo latin clause to the end to put it all in perspective.
Malleus Maleficarum: Unfortunately not one of our textbooks, but fascinating nonetheless. The "Witch Hammer" was the medieval equivalent of the US Government's Bluebook report on UFO's, except this was in 15th century Inquisitive Catholic Germany and was arguing (vehemently) for the existence of witches. And, naturally, for their subsequent dis-existencing.
That's enough for now; I don't wanna scrape the bottom.
[Edit: I *knew* it. I was deciding between using dishes in the sink and a thong on the couch as an example and I figured "in re: red thong" sounded funnier but wondered if people were going to assume there's a story behind it. I'm sorry to say there's not, Anja. You can convey the disappointment to your mom. ;-)]