To "
case a joint" is to check out the details to, and make speculations about, a home,
car, store or other location for means of getting in undetected and/or removing material from
said location.
Usually referred to negatively as a means to describe being suspicious someone is going to steal someone's belongings, it can also simply be a synonym for reconnaissance.
1. That
banger over there was casing the joint when I came in this
morning.
2. Tell Tommy to go case the Sanders' joint and see if Paulie's
car is there.
3. I saw you going out to case a joint earlier, you better not take anything.