How does the insurance co. come up with the KBB of a car?

I wrecked my car last week and it is totaled. I have full coverage with a $1000 deductible, so I'm uming I will get a check for the KBB value of my car? My question is how do they tell what the value of my car before the accident would have been, as the ins. company had never seen my car in the condition it was before the wreck.