Utilitarianism considers precedent to be important, but does not offer any method of determining exceptions. It is impossible to determine how much effect on precedent any given isolated action will have. In the case of determining whether or not to torture the terrorist, one must consider whether it is good for society to allow torture to be used as a method of gaining information. If it is bad, one must determine whether this action will create a precedent. If it will create or contribute to the creation of a precedent, one must compare the detrimental effects of this precedent with the other consequences and welfare caused by the action.
Utilitarianism offers no method for comparison.
The problem is that a person faced with making the decision cannot get the information. Even through experience, it is hard to judge how much effect each action has on precedent. More specifically, it is hard to determine whether an action is worthy of being an exception to a rule. Utilitarianism offers no resolution to this problem. Utilitarianism also considers the Theory of Desert to be instrumentally valuable to the promotion of happiness.