Interesting question. You don't need to cite cases in the essay section of the law exam. If it's a landmark case, you just use the name like Roe v. Wade and that suffices. The bar examiners aren't looking for citing the law--they're looking at how well you can apply the facts to the law and demonstrate how you can see both sides of an issue since lawyers are required to do that in real life. Rumor has it that you can even make up a law just as long as you demonstrate this skill, however, I would not advise that you do so.
