When citing a U.S. Supreme Court case, you must cite to the official reporter, the United States Reports.
A citation to a case in the United States Reports includes the following five elements:
You may need to include a "pinpoint" citation, which is a citation to the page(s) on which the specific material referenced appears. If you need to include a pinpoint citation to, for example, a quotation or the holding of a case, add the page number after the first page.
New York Times Co. v. Tasini, 533 U.S. 483, 491 (2001)
(This information adapted from Georgetown Law Library Guide to Citing Cases)