Increased critical strike chance against enemies on full life

If a critical strike is only rolled once per casting and the result is applied to the entire spell, how does the conditional increase of critical strike chance relate to all of this?

Does it mean the calculator rolls a 1d100 and says "If your critical hit chance is equal to or greater than this rolled threshold, this hit is a critical"? And then it compares the threshold to the basic version of CsC and to the conditionally increased CsC separately on each hit?

Or does it mean that if the base version of CsC is not enough, the spell is not critical, and if the condition is met during the duration and the conditionally increased CsC is enough, the spell becomes critical for the rest of the duration?

I think the keyphrase on poewiki for Spell Echo is "Critical strikes are rolled once". Since it won't re-roll on subsequent repeats, the spell shall continue to crit until the last repeat even though the enemy is no longer full life after the initial hit.

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jeerinho wrote:

I think the keyphrase on poewiki for Spell Echo is "Critical strikes are rolled once". Since it won't re-roll on subsequent repeats, the spell shall continue to crit until the last repeat even though the enemy is no longer full life after the initial hit.

Thanks, that solves 50% of the problem. So once a spell is considered critical, it stays critical.

Now I would like to find out how the calculator decides whether to use base CsC or conditionally increased CsC to decide whether or not a spell is critical. Will the first hit decide? Does this mean that an assassin's mark hit can increase the CsC of the entire spell, while the assassin's mark has no effect if another target is hit first?