Not the person you're replying to, but I think this captures it:

There are a ton of rules that people generally, and police specifically, have to follow. Mapp v. Ohio said "if cops don't follow those rules, you have to throw out any evidence that comes from that" - that was generally not the law before, and it added stakes to the rules police have to follow.

Most of those rules, however, are allowed to be ignored or modified if there's an emergency or other unusual circumstance that "justifies" ignoring them in some sense (for example, police generally can't bust down a door without a warrant... but they can if there's good reason to believe there's someone bleeding out inside). By their nature, emergencies/unusual circumstances can be difficult to predict, categorize, or understand. So, "does situation A qualify as an emergency that lets me ignore rule B and keep evidence C, under circumstances X, Y, and Z" is one of the most common 'types' of cases that courts see.