Sorry to say, but some folks don't clean up after themselves.... what I mean is that some loaders who know their brass is done and should be put in the recycle can will leave them on the ground and don't care.
That behavior is bad because folks who do pick up range brass could be affected. If that brass is about to fail, then the right thing to do is put it in the scrap recycle bin, not leave it where some rookie gets hurt.
At the same time... If you are a rookie and picking up range brass, it is your responsibility to inspect the brass very well to eliminate ones that are near failure.
@18trapper , a crimped primer is an indicator of once fired brass, but even then you should inspect all brass that wasn't yours.
It is best when you actually witness the source, like the LEO practice days or other shooters who leave their factory brass. When that isn't the situation, consider it your standard operating procedure to thoroughly inspect unknown brass, but you should always inspect all brass that hits the ground anyway.
This is the right place for good cleaning and a borescope, or bent paperclip, or section, or all three. Taking the ones that seem the worse and cutting them open is a good way to know what you are dealing with. Play it safe with any brass that hits the ground, especially if it wasn't yours.