Language of crime

Author: Marta Sánchez-López is a PhD candidate at the Dept. of Linguistics and Basque Studies (UPV/EHU), The Bilingual Mind research group.

What if I told you that language can incriminate you? Yes, it is true, the way you speak tells so much about yourself. Humans use language to communicate about events of the world and there are different linguistic communities: Spanish speakers, Basque speakers, English speakers, etc. But, do all speakers of the same linguistic community speak in the same way? Obviously not, language will vary depending on your social background, the place you live, your educational level, and many other factors. Hence, each speaker has a specific use of language. You may ask what is this important for? Well, it is much more relevant than what you believe. Imagine that someone always says an expression wrongly, everyone around him knows but, he is not conscious of it. Here comes the plot twist, this “someone” was a criminal, and he was arrested thanks to this peculiarity. And yes, it was a real case! This was the Unabomber case.

This photo, released by the U.S. Marshals Service, displays one of the lots being sold in an online auction in 2011 of the personal effects of Ted Kaczynski, aka the “Unabomber.” Proceeds from the auction were used to compensate Kaczynski’s victims. This is Kaczynski’s handwritten rough draft of “Industry society and its future,” which was ultimately published in 1995 in the Washington Post and New York Times.

Ted Kaczynski sent several mail bombs in the United States from 1978 to 1996. At the beginning, the police thought that the criminal would be an aircraft mechanic, but they did not have a clear suspect. Kaczynski published a manifest explaining his thoughts: Industry society and its future; and, this was his downfall. His brother saw the document and noticed a subtle detail: he recognized a sentence that Kaczynski usually said: You can’t eat your cake and have it too. Kaczynski used that expression incorrectly (the correct form is you can’t have your cake and eat it too).This peculiarity of his use of language helped the police to arrest him. Thereby, the police realized that he was not an aircraft mechanic, but a mathematician (Queralt, 2020). All in all, we can say that language gave him away.

At this point, you may think, right, one case in which language has been important, but, it is only one case! On the contrary, these linguistic peculiarities have been useful in many criminal cases. Next, I will show you another interesting case.

As I previously said, the place you live and your educational level affect your language (and can also give you away!) as happened in 1979. A little girl was kidnapped; the police considered several authors but they did not have a guilty. They had a note from the kidnapper and they decided to show it to Roger Shuy, a linguist. Shuy read that letter and suggested that probably the kidnapper was from Akron, Ohio, and he had a high educational level. These conclusions were enough to reduce the number of suspects to one. Shuy knew that the kidnapper was from Akron, Ohio, because he used the expression devil strip, commonly employed there, to describe the small patch of land between a sidewalk and a curb. In addition, albeit the kidnapper was trying to hide his high educational level using some orthographic mistakes such as *kan (instead of can)or *kops (instead of cops), he wrote perfectly more complicated words such as precious (Queralt, 2020).

Language can be useful as a tool for investigations also after the arrest. Another factor that has an impact on language is personality traits. The language of people diagnosed with psychopathy reflects its features of it. To go deep into this question, Marko and Leibetseder (2023) carried out research to determine whether psychopathy traits are reflected in language. They analysed private letters of Jack Unterweger, an Austrian killer. Unterweger was accused of several women murders during the 1970s and the 1990s. Once he was arrested, psychiatrists diagnosed him with psychopathy. Unterweger wrote many personal letters that ended up as the corpus of study for Marko and Leibetseder. They looked at these letters to determine whether psychopathic characteristics were reflected in his language (Marko & Leibetseder, 2023). And it was!

Psychopaths are manipulative. They use strategies to get what they want through manipulation. They use people as instruments to achieve their aims. This trait could be reflected in the use of directive speech acts in the letters. In Unterweger’s letters, direct constructions were used more frequently than indirect ones (Marko & Leibetseder, 2023). Example in (a) shows an example of a direct use where he described a manipulation:

  1. I have to think about earning money, do readings and some toiling to make sure that I receive invitations for readings in June and at the beginning of July! (Marko & Leibetseder, 2023, p. 54).

Other psychopathic traits are coolness and lack of coherence, also reflected in his letters. Unterweger used the third person for referring to oneself, reflecting an estrangement from the event (Marko & Leibetseder, 2023):

  1. That it makes a difference to write to the inmate, visit him in jail or encounter [him] in freedom (p. 58).

Unterweger showed incoherence in his letters despite the fact that he was also a well-known writer. He concatenated unrelated thoughts (Marko & Leibetseder, 2023):

  1. Additionally, what I do not like, also is wrong, but reoccurs throughout, I wonder why, to show, see, I am decent, … (p. 59).

This type of study contributes to the production of linguistic profiles that will be useful for future investigations.

The gist of all these cases is that language is not only the tool we use to communicate, but it tells much more about us (and sometimes it can even give you away!).


Queralt, S. (2020). Atrapados por la lengua: 50 casos resueltos por la lingüística forense. Larousse.

Marko, K., & Leibetseder, I. (2023). Linguistic Indicators of Psychopathy and Malignant Narcissism in the Personal Letters of the Austrian Killer Jack Unterweger. Forensic Sciences, 3(1), Article 1.

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1 comment

  • Forensic linguistics has come a long way and has been refining its techniques over the past decades. However, it has not yet gained full recognition in court, like other forensic techniques (dactyloscopy, ADN…), due to certain shortcomings. It is very useful when the investigator has to choose from a small closed pool of candidates, but as the number of suspects increases, its accuracy dwindles. In any case, it is to be hoped that with the recent advances in AI its results will improve and it will consolidate as a fully reliable judicial test.

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