Yeah. To follow up (and try to explain it in a way dumb people like me will understand) the US is big on "precedence", which essentially means if a court says, "We believe this law applies this way in this specific scenario" then another court can and likely will reference that previous decision while making its own ruling on a completely separate (but somehow related) case.

As a hypothetical example, imagine a court 50 years ago said that talking to the police after invoking your 5th Amendment rights nullified your invocation of your rights.

Then, a case appears where a suspect wasn't read his Miranda rights but had invoked the 5th, except he then spoke to the police immediately after (and nullified his previous invocation). Well, what if the court decides he can re-invoke his 5th Amendment rights once he's finally read his Miranda rights? Boom. More precedence.

See how it can get complicated? It's almost kind of like when you have to write a bunch of edge-case code because weird "gotchas" keep cropping up and it's a bitch to rewrite the entire thing.

Best i can tell it is not just that it will be referenced, but that judges on the same tier of court is bound by that decision until a higher tier overrules it.

This process btw is how USA effectively got software patents.

A corporation or other applied for a patent on a production process that used a computer (and therefore software) to gain more precise control of the results than previous mechanical means.

The patent holder was sued over it, and a judge ruled in the patent holders favor.

This ruling was then used by other lawyers to press for "process" patents, where the process was described in software.

And so far no higher court has overruled the initial ruling, thus effectively USA have software patents.

Judges on a tier below a decision are bound by the higher court's ruling. This is mandatory precedent.

Judges on the same tier are not strictly bound, but in the interest of consistency (the law always seeks to be applied in the same way to the same situation), will look to the rulings of other courts on their level if no higher court has ruled. This is called persuasive precedent. The Supremes often take a case because the lower courts, (Circuit Courts of Appeals) have ruled differently on the same issue. This is called a circuit split.

Would be helpful if you cited the case, since patent law is an interesting example of a lower tier court going around the supreme court. It was pretty clear (except maybe to a lawyer) with Gottschalk v. Benson that software should not be patented, but that never stopped the federal circuit from working around that little problem... (http://www.ipwatchdog.com/2012/03/20/supreme-court-mayo-v-pr...)

I believe it was a case involving State Street Bank in the mid nineties.

IANAL, nor American, just going from memory.

Thanks for the clarification. The precedence system was known to me, but to have it explained in this way became instantly understandable.

Coming from a civil law country (where precedence does not play that much of a role) really makes these things hard to grasp normally.

Why would civil law systems be simpler? Wouldn't the civil code have to essentially hard-code just as many edge cases? Or are those systems OK with unpredictable outcomes for such cases?

I'm not sure they are always simpler, but it's easier to get a simpler flow when you can reformulate it, instead of having to rely on the accretion of decisions on specific issues.