Linguistic Fingerprints?
How language analysis helps solve crimes.
Posted August 3, 2025 | Reviewed by Jessica Schrader
An anonymous bomb threat is phoned into a school. A lengthy manifesto inciting violence is posted online under a pseudonym. A series of texts is sent from a missing person’s phone, but the person never turns up. These are all cases involving language evidence.
But how can evidence like this help police? Just as there are scientific experts in fields like anthropology or pathology who examine physical evidence, there are also language scientists who analyze language evidence.
What is forensic linguistics?
Forensic linguists use their knowledge of language sounds, meanings, and dialect patterns to come up with demographic profiles of speakers or writers as well as assess their emotional and psychological states and intentions. They also compare anonymous writings and voices with those of suspects, to help identify perpetrators.
All languages and dialects, even those considered nonstandard, have regular rules and patterns, most of them unconscious and some of them quite subtle. Sometimes hidden patterns can help unmask anonymous speakers and authors, as happened in a famous case involving a serial bomber.
The linguistic profile of the Unabomber
The Unabomber was an anonymous serial bomber active in the U.S. from 1978 to 1995. His bombs were usually sent by mail and were sometimes accompanied by notes. All told, his bombs killed three people, injured 23, and caused fear throughout the nation.
In June 1995, he sent a 35,000-word typewritten manifesto to the media in which he outlined his grievances against modern society. Clearly, this is a case involving language evidence—lots of it.
During the investigation, the FBI combed through the Unabomber’s words, looking for potential indicators of region, age, education , or other factors to help create a so-called linguistic profile.
Dr. Roger W. Shuy, a leading figure in forensic linguistics, suggested that the bomber could be traced to the Chicago area, given his use of unusual spellings that were once standard in the Chicago Tribune , for example, “instalment” for “installment” and “analyse” for “analyze.”
Investigators also felt that the bomber’s vocabulary choices pointed to an older male, since he used old-fashioned, sexist terms for women like “chick” and “broad.” His grammatical and formatting choices also indicated someone who was quite well educated.
A key suspect and an author comparison
As the investigation proceeded, the profiling task turned into one of author comparison, or authorship attribution, as the FBI compared the bomber’s writings to those of a number of suspects. At first, no matches were found.
Almost 30 years ago—in September 1995— The Washington Post published the Manifesto, at the urging of law enforcement. Several months later, a man by the name of David Kaczynski contacted the FBI to report that the writing style seemed to match that of his brother, Ted Kaczynski.
Kaczynski, as it turned out, was a 53-year-old male with a Ph.D. in mathematics born and raised in the Chicago area. If his writings could be shown to match those of the Unabomber, the linguistic profile would prove spot on.
The FBI compared the Manifesto with letters and articles authored by Ted that were provided by his brother and other family members.
The unusual spellings matched across the anonymous and known documents, and investigators also found other commonalities, for example, distinctive or unusual words and phrases like “cool-headed logicians,” “chimerical,” and “middle-class vacuity.”
Finally, they hit upon a “linguistic smoking gun”: The head of the FBI’s comparative language analysis, Supervisory Special Agent James R. Fitzgerald, noticed that both Kaczynski’s and the Unabomber’s writings contained the phrase “can't eat your cake and have it too”—backwards from the typical wording in American English: “can't have your cake and eat it too.”
Fitzgerald and his team compiled all the common vocabulary, spelling, grammar, formatting, and phrasing consistencies across the document sets, and this list formed a central part of the 50-page affidavit used to obtain a search warrant of Kaczynski’s isolated Montana cabin.
The search yielded extensive evidence tying Kaczynski to the Unabomber—and proof that forensic linguistics can be used to accurately profile and identify anonymous authors.
In the years following the Unabomber investigation, forensic linguistics has been used in numerous criminal cases involving speaker and author profiling and comparison, as well as the analysis of interview discourse and witness statements.
Nowadays, there is a growing need to identify anonymous authors on the internet and in social media , as well as to examine language style for indicators of genuine intent to do harm (as opposed to idle threats). And there’s an added wrinkle, as forensic linguists are now also called upon to assess whether authors are humans or AI —or humans using AI to perpetrate scams.
The primary channels of (nefarious) communication may have changed over the decades, but people—and computers—still give themselves away with the unconscious usages that comprise their unique linguistic fingerprints.
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Natalie Schilling, Ph.D., is a linguist specializing in forensic linguistics, sociolinguistics, and dialect variation.
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This article is part of the Bringwise Psychology Journal — daily insights on human behavior, mental health, and personal growth.