You know, some folks might think grammar isn't important in this business, but that just isn't true.
You've got to know the difference between whose and who's in order to get to the bottom of a mystery.
"Whose" indicates ownership. For instance:
Whose sword is this?
My intuition tells me it must belong to someone whose arms can hold a giant, metal sword.
"Who's" is the contraction of "who is". For instance:
Who's responsible for this?
Well, I think we know who's guilty.
Case closed. Who's the best cop in town?
Are those donuts I smell? Whose are those?