With legal research, case refers to the written decision/opinion of a judge or group of judges. These written decisions serve as precedent-- that is, they will be important to subsequent decisions.
Courts whose decisions are published are almost always appellate courts. Many cases' decisions will only be available at the courthouse where the legal proceedings were held.
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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.
Good places to start:
With a Google search of court records and the county and state the crime was prosecuted within, sometimes you can find a county website that will provide court records.
This will be hit or miss: Some will be available electronically, others not. Some will charge for these records, others not.