Have you see Google’s Ngram Viewer (http://books.google.com/ngrams/), which charts word usage over time for a pair of words? Well, there is a new (and free) database called Legal Language Explorer (beta), http://legallanguageexplorer.com/,  which does something similar for words and phrases used in U.S. Supreme Court decisions.  At Legal Language Explorer, you can run a search of one or more phrases (each phrase can have up to four words) and it will generate a time-series frequency chart of each phrases’ appearance in Supreme Court opinions between 1791 and 2005.  There are also advanced features including normalization and alternative graphing tools.

You can search any phrase you want. A few ideas are:

Clear and Present Danger
Habeas Corpus
Custodial Interrogation
Due Process

The project is a joint venture between Michigan State College of Law and Emory Law and the website has links to their research paper on SSRN.