Prompted by another thread.
Admiral Screed: Once per activation, when a friendly ship is attacking, it may spend 1 die to change a die to a face with a [CRIT] icon.
It doesn't specify who's activation, just once per activation. Seems to me that if one of my ships were to get an attack during the other player's activation, I would be allowed to use Screed.
I can only think of this being useful under a very specific case, but I can't see any reason I wouldn't be allowed to use it.
(In case anyone's wondering, It would be QLT, Kallus, and something that would make crits relevant, such as Flechette Torpedoes, or PDR, or black dice)