So critical hits don't count defense boosts while calculating damage.
However, they do count defense drops.
Say a Pokemon has +1 defense, from using eg. Harden. Then, their defense is lowered by a move such as Tail Whip - supposedly putting them at +0 defense, back where they started.
They are then attacked. Since defense boosts are ignored but drops aren't, would the attack's damage be calculated with the defense at -1? or would it use the normal defense stat ( +0 ) ?