Experiments can be found in the Experiment cave, which can be accessed during Creature of Fenkenstrainquest. Completing the whole quest is not required to kill them, as you can simply push the farthest memorial from the castle and you will enter finding quite a few of them. In total, there are 18 Experiment spawns in the cave: 7 Sheep-dogs, 5 Spider-men and 6 Wolf-women.
The Wolf-woman may only be killed during the Creature of Fenkenstrain quest. Attempting to kill one afterwards results in the message "You don't have the heart to kill the poor creature again."
An Experiment must be killed to complete the "Lab Clean-up Assistant" Morytania task.