How does forensic linguistics/stylistics work in criminal issues?
When criminal activity includes written or spoken communications, experts can analyze the habits of the writer or speaker, and from the principles of habit in using language can observe details of syntax, vocabulary, slang, alternate spellings, etc., to build a “profile” of the communicator – educational level, ethnicity, even the mood when the communication was sent. Equally important, analysts can compare one written/spoken communication with another to determine the authenticity of authorship. For example, if a letter is suspected of being a forgery, expert analysts can compare it to established examples to determine its authenticity. If someone disclaims authorship, changes in language usage can be pointed out, as evidence.