KD, I remember that the "red" needed to have as many skill points as possible. A "red" with only 500 skill points might not give a justice gain, but one with 720 skill points probably would. I should get my red back to HQ1 as she has the full 720 points.
Also UO guide says the time to wait in between getting points is 5 minutes. We could test this. I know I recently was letting someone get points, and I'm sure they didn't wait the full 7 minutes, but then I wasn't checking their points.
Here is a link to a summary at UO guided:
http://www.uoguide.com/JusticeGaining Justice
Justice is awarded to the person who delivers the killing blow to a murderer, or red, character in Felucca. There is a timeframe of 5 minutes between being able to receive Justice again. This is to prevent people from "farming" Justice by continuously res-killing a red.
The amount of Justice gained from each kill varies with the amount of skill points of the killed character and the level of Justice their killer is currently at. After each kill, a message stating "You have gained in Justice" will be displayed. Once you have fully maxed out the number progress points you can earn a message will be displayed stating "You cannot gain more Justice" which for Justice is two kills past reaching the Knight level.
Roughly speaking, killing a skill capped murderer will award up to 3 progress points while attaining Seeker of Justice, a point and a half while working towards Follower of Justice and a point for each kill while attaining Knight level.