Source: http://win.wizkids.com/bb/viewtopic....1ccb7190b8629a

It Is The Most Logical Course Of Action...The Probability If Success Being Approximately 83.33%: FREE: Choose a friendly character within 4 squares and line of fire. The next attack roll that character makes this turn can't be rerolled and on a result of
2-4 the attack is a critical miss.
5-12 the result of the attack roll is 7.


The rules except on Critical hits read

If the attack roll was a physical twelve (6- 6), all targets of the attack become hit, even if the attack total would normally miss one or more of the targets. This is called a critical hit. A critical hit increases the damage dealt by 1 to each hit target when dealing damage.


If I roll a "physical" twelve and Mr. Spock changes the result of the attack roll to a 7 is it still considered a critical hit?

WK: Yes. Mr. Spock's effect changes the result of the roll, not the actual roll itself. Note that the result will be considered a 7 and will be added to the character's attack value for any effects that check for attack roll results or attack totals, but the attack will be a critical hit and cause all targets to become hit and deal the extra damage accordingly.

Note that the same would apply to a roll of doubles. The result would become 7, but the attack would still gain KNOCKBACK.