The phrase dead to rights is basically synonymous with red-handed, but it's a far weirder expression. It was first recorded in 1859 in George Matsell's Vocabulum, which compiled a list of New York criminal slang at the time. Matsell noted that a lot of their vocabulary was beginning to seep into public usage through newspapers, and this one certainly did - by the mid-1870s, it was widespread. In this, both the words dead and rights have different definitions than usual: dead means "full" or "complete", as in dead stop or dead silence, and to rights was an old prepositional phrase meaning "in proper order". Together, to have someone dead to rights is to have someone fully and properly caught. Search and literary frequency of dead to rights has steadily been increasing, possibly because of its use in crime dramas.
Adam Aleksic, a rising sophomore studying linguistics and government at Harvard University, has been described as the internet's sixth most famous etymologist. He also has disturbing interests in politics, vexillology, geography, board games, conlanging, and law.