Have you seen this man?
Probably.
This is one of the most famous police sketches ever made, and it's supposed to be this guy, Ted Kaczynski, aka the Unabomber, an American terrorist who mailed homemade explosives across the country for almost 20 years.
Obviously the sketch artist didn't have much to work with, and the Unabomber left no fingerprints or DNA. So how was he finally caught?
Linguistics.
I'm Erika Brzozowski, PhD, and this is Otherwords.
When the Unabomber sent a 35,000-word manifesto to the newspapers, the FBI had forensic linguists James Fitzgerald and Roger Choi examine it for language clues.
They found some outdated terminologies like broad and chick that weren't likely to come from a woman or a young person.
Arcane words like anomic and chimerical suggested a high level of education, and they knew that odd spellings like willfully and clue were briefly popular in the Chicago area in the 40s and 50s.
In 1995, Linda Patrick was reading the manifesto in the Washington Post and found it disturbingly familiar.
