Adeptus-B said:
'Carte blanche' is boring . It's much more interesting from a storytelling perspective for PCs to have to carefully consider the consequences of their actions.
I find my self in agreement with this. That said, there is difference between realistic consequence, fun consequence, and ******* GM consequence.
In this case what would might be interesting would be Kill-Team to be gathering evidence before they make there move, and then presenting the information to their Watch-Captain. Either before the deed and get the Watch-Captains approval, or afterwards at an inquiry performed by the Deathwatch.
The key here, is too neither allow playing to run wild as cowboy cop marines but at the same time encourage them to take an active interest in what NPCs do.
Essentialy by playing smart and being prepared the players should be able to avoid most reprecussions for the act.