As I recall, the casuality rate has something to do with that:
None = no injured no matter what the result
Low = can injure on Disaster
Medium = can injure on Failure + Disaster
High = can injured on Success + the previous two
Extreme = can injure no matter what the outcome
Adjust based on random Doff, and if the Doff is white or not (white can be killed, though not always). And also note, I don't know if this is accurate or not; it's just my take on it.
But I think this is why Strike At Fugutive Network always injuries at least one Doff.