APA style citations typically include the author's last name and the year of publication. Legal sources such as criminal cases clearly cannot follow this same format, so the "Publication Manual of the American Psychological Association" (6th edition, 2nd printing) explains the format you should use in citations and on the References page for court cases.
Citations in the text of your paper allow your reader to find the full citation entry on your References page, which gives all the information the reader needs to physically locate the source. The easiest way for your reader to find information about a criminal case is through the name of the principals involved and the year. The names appear in italics in the text with a "v." between them (without the quotation marks). You may place the source in a signal phrase like this: As illustrated in Minnesota v. Smith (italicized) (2005). Alternatively, you can place the information in a parenthetical citation: (Minnesota v. Smith [italicized], 2005).
The entry for a criminal case on the References page begins with the name of the case -- the names you cited in the text of the paper. You should still put the "v." between, but do not italicize the names. After a comma, list the volume number, the abbreviated source and page with no punctuation between. After a space, the abbreviation for the court and date of the decision appear in parentheses. The entire entry ends with a period. Such an entry might look like this: Minnesota v. Smith, 247 F. Supp. 955 (Minnesota 2005). This entry comes from the "Federal Supplement," volume 247 and page 955. The decision was set down by the federal court for the district of Minnesota in 2005.