 Davy became a Serjeant-at-Law on 11 February 1754, and soon after became involved in prosecutions under the Black Act.In 1762 he became King's Serjeant, then the highest accolade for a barrister.Davy argued that "the air (of England) is too pure for a slave to breathe in" when he represented James Somerset, an escaped African slave come from Boston whose London godparents had sued for a writ of "Habeas Corpus", in "Somerset v Stewart".