Guidelines for references to legal materials can be found on pages 216-224 in the 6th edition of the Publication Manual of the APA. In text, cite the name of the case in italics, and the year of the decision. If two or more years are given, cite those years as well.
Here is the form for cases:
Name v. Name, Volume Source (Court Date).
Abbreviate the published source (if any), court, and date. Here is a sample References entry to a case:
Lessard v. Schmidt, 349 F. Supp. 1078 (E.D. Wis. 1972).
Here is a sample text citation:
Lessard v. Schmidt (1972).
Explanation:
This decision was rendered by the federal district court for the Eastern District of Wisconsin in 1972. It appears in volume 349 of the Federal Supplement and starts on page 1078.