I was reading George Orwell's essay "Raffles and Mrs Blandish" and came across this quotation,
"Some of the early detective stories do not even contain a murder. The Sherlock Holmes stories, for instance, are not all murders, and some of them do not even deal with an indictable crime. So also with the John Thorndyke stories, while of the Max Carrados stories only a minority are murders. Since 1918, however, a detective story not containing a murder has been a great rarity ..."
I was wondering at what period do historians of the detective fiction genre put this shift to murder plots from broader crime plots. Orwell puts it at 1918, but I can imagine experts on the genre disagreeing with that date.