maybe it's kind of random..
or maybe it has to do with previous shots taken by the same shooter...if the defender can't realy hold off the shooter, he might get frustrated and foul him next time...
dunno. I din't realy look into it for my team, but it apeared to me it was kind of random...
They are not your friends; they dispise you. I am the only one you can count on. Trust me.