Whenever an attack is made, all Critital % improvements are totaled. A D100 is rolled against the final sum Critical %. If the die is rolled under the Critiacl %, a Critical Hit is scored and the damage is increased based on the two damage multipliers for the attack type. This multiplication is done before armor soak is applied.
All attack types have a pair of Attributes or Skills responsible for their damage multiplier. Melee attacks use Strength and Focus, Grenade attacks use Willpower and Focus, Sniper Rifles use Stealth and Focus and all other ranged attacks use Quickness and Focus. Every point added to a damage multiplier stat increase Critical hit damage by 7%.