How Forensic Linguistics Works

This week's video explores forensic linguistics, using the Unabomber Manifesto as a prime example. The manifesto, "Industrial Society and its Future," inadvertently revealed its author's identity through subtle linguistic clues. For instance, Ted Kaczynski's use of "broad" and "chick" for women suggested he was in his 50s and had withdrawn from society by the late 1960s. British spellings like "license" hinted at a Chicago upbringing, aligning with the Chicago Tribune's past promotion of such spellings. The dissertation-like structure of the manifesto further indicated his educational background. These clues, along with reversed idioms, led authorities to his cabin, marking a significant case solved by forensic linguistics. The video then delves into how forensic linguistics works, starting with identifying authorship. For lengthy texts, "Burrow's Delta" is employed. This method compares the frequency of the 500 most common non-story-specific words between texts. A famous non-criminal application involved J.K. Rowling, whose pseudonym Robert Galbraith was unmasked by comparing word frequencies in her known works and Galbraith's novels, revealing a strong stylistic match despite genre differences. For shorter texts, like ransom notes or text messages, the "Jaccard coefficient" is used. This technique identifies distinguishing linguistic features between known texts from different individuals and then calculates a similarity score for an unknown text. This was crucial in a 2005 UK murder case where a missing girl's "runaway" texts were matched to her boyfriend's writing style, leading to his conviction. Even without a suspect, linguistic clues can be vital. A kidnapping case in Illinois was solved when a forensic linguist deduced the ransom note writer was a well-educated man from Akron, Ohio, based on unique misspellings and the regional term "devil strip." Forensic linguistics can also analyze confessions. In the Timothy Evans case, inconsistencies in his confession's sentence structure suggested police influence in the incriminating parts, highlighting how linguistics can uncover external factors in written statements. The video concludes by promoting Wild Grain, a sponsor offering baked goods.