Does an injured deer die?

It depends on the severity of an injury, a gash may heal, a fracture may mend, but a broken leg will most likely ultimately mean death in the wild unless they're taken to the vet. The gash may always fester and become infected though. If it's hit by a car then it's likely going to die unless it was hit at like 5-10 miles an hour. Side note: I saw a deer get hit by a car going 70 miles/hr the other day and it was insane. The front wind shield was absolutely obliterated and the deer went flying high into the air- I'm almost positive it didn't survive.

Sadly in most cases that go untreated yes. Though it would depend on the seriousness of the injury.

Sometimes

I think so. If its hit by a car... most likely it will die soon

If something is effecting anything in a bad way, that thing will eventually end.

Define "injured"!

Boo-boos don't kill anything,being smashed does.

Every living thing dies sooner or later.

sometimes yes