There's a whole field of "forensic linguistics" that deals with language, criminal justice and dispute resolution. They do use corpora, although they may not use methods as sophisticated as the ones we use. Anything they find has to hold up in a court of law, or else force a settlement or plea bargain.
This past spring at the International Linguistic Association in New York, we had a lecture by James Fitzgerald, a former FBI agent who used corpus methods to help catch the Unabomber. This Language Log post talks about some of his work:
http://itre.cis.upenn.edu/~myl/languagelog/archives/002762.html
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-Angus B. Grieve-Smith
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