To find case law, you'll need to know the court from which the opinion originated. U.S. Supreme Court opinions are very easy to locate. Lower federal and state courts can be a bit more difficult.
Information on which court heard your case can often be can be gleaned from the citation of the case or from a quick Google search.
After you know the court your case was argued in, use the sub-tabs to the left to locate case law resources from: the U.S. Supreme Court, US Circuit & District Courts, State Courts, Pennsylvania Courts.