You need hardly any time at all to study your targets before making a death attack.

Prerequisite(s): Perception 11 ranks, Eye for Death, death attack class feature

Benefit: You need only study your victims for 1 round before being able to make a death attack against them. If you do not launch the attack within 4 rounds of completing the study, 1 new round of study is required. You may increase the DC of the saving throw to resist the death attack by 1 for each additional round you choose to study your opponent, to a maximum of +2 from 3 total rounds of study.