Author Identification

Linguistic analysis of a document by an unknown author can determine some of the author's characteristics. This analysis is unlikely to identify a particular person, but may help narrow a pool of suspects or provide evidence about whether a defendant wrote the document. The characteristics that can be determined by linguistic analysis include the following:

First language. Is the author a native speaker of English? If not, are there clues to what the author's first language might be?
Age. A younger person is likely to have a less sophisticated writing style than an older one. A threat with no apparent motivation may be an indication of a younger person.
Ethnicity. Is the author a competent speaker of
African American Vernacular English? Or does the communication include any terms associated with a particular immigrant community? For example, "Desi" used to refer to a South Asian, or "Pinoy" for a Filipino.
Education. Or more accurately, writing ability, which generally increases with more advanced education. The analysis for educational level looks not only for spelling and grammar mistakes, but the level of sophistication of the structure of individual sentences and the document as a whole.
Occupation. Use of jargon may indicate the author's occupation. For example, civil engineers make a distinction between a tunnel and a tube, whereas other people might not be so careful about such terminology.
Motivation. The motivation for a communication may not be obvious at first glance. A letter might be a ruse, written to misdirect investigators. A threatening letter may have been sent by the victim herself.
Geographic origin. Use of regional dialect terms or constructions may reveal where the unknown author grew up.
Gender. Men and women tend to write about different topics and in different ways.