Actually, I think this only works with 8 pills, one of which is poisoned.

Take any six pills, put three on each side. If one side of the six weighs more, you have narrowed it down to the three pills on that side.
1) If it's even, none are poison, so weigh the last two to find the poison one. 2) If one side weighs more then take any two from that side and see which is heavier. If they're equal, it's the one you left off.

(If there are 9 pills, your inital weighing might leave one heavy side with 4 pills. There is no way to find the outlier with only 1 more weighing.)

p.s. If anyone doesn't get it, I'll post again with more details.