Queen on Sayers
Dorothy L. Sayers, Unnatural Death, 1927
'Yes. Now, look here. S'posin' you take a good big hypodermic, empty, and dig it into one of the big arteries and push the handle - what would happen? What would happen, doctor? You'd be pumpin' a big air bubble into your engine feed, wouldn't you? What would become of your circulation then?'
'It would stop it,' said the doctor without hesitation.
Ellery Queen, The Siamese Twin Mystery, 1933
"You're too captious, my boy," went on Dr. Xavier. "Read a story once in which murder was committed by injecting the victim with an empty hypodermic. Coronary-explosion sort of thing. Well the fact is, as you know, death won't occur from that cause once in a hundred times. Didn't bother me though."
Sayers on Queen
Ellery Queen, The Greek Coffin Mystery, 1932
Certainly the revelation of an apparently reputable young man, an Assistant District Attorney, as the prime mover in a series of crimes engineered with profound imagination and supreme insouciance must be confounding if you don't know how and why he did it.
Dorothy L. Sayers, Busman's Honeymoon, 1937
Why, come to think of it, Mrs. Kirk had been reading a book only the other day in which one of the police in charge of the case turned out actually to have done the murder. He distinctly remembered laughing and saying, 'It's wonderful what these writer-fellows think of.' That Lady Peter Wimsey, who wrote those books - she'd be ready enough to believe a tale like that.If you want to say, a district attorney isn't a policeman, you're right, of course; but unlike English prosecutors, they are often depicted as involved in or in charge of the investigation, as in this case.
Update: also this, from earlier in the book:
'I read an American story once, and the way the police carried on - well, it didn't seem right to me.'