The text of the U.S. Constitution is widely available through a variety of sources. Searching for the text of the Constitution affords a rare case in which a simple web search for "constitution" will suffice. Most sources will work as well as another because unlike references to statutes, court decisions or most other authorities, Bluebook rules provide that a citation to a current state or federal constitution need not provide a source or a date.
That said, the following are select sources of the text of the Constitution:
Because of their annotations, some of the more useful versions of the U.S. Constitution are published as a part of the unofficial editions of federal statutes:
These annotated codes are a good place to start your case law search. For each relevant article or section of the Constitution, first reference the "Notes to Decisions" on Lexis and "Notes of Decision" on Westlaw for a list of cases curated by the editors and organized by topic. Next, reference the cases listed via the citator tools ("Citing References" on Westlaw; "Shepardize" on Lexis).
Absent a specific Constitutional article or section, there are four recommended methods for identifying cases: