In the RRG it says you may trigger a crit effect and that every ship has a base crit effect of first card face up. Consider the scenario you have a corvette with med team and no shields. You have rolled 1 crit 3 hits after the spend defense tokens is over. I am assuming you can choose not use the crit effect to just deal 4 facedown cards and not risk the med team triggering.
Edited by SlappyWhite