Dorothy L. Sayers said this quote

But if you were investigating a crime,” said Lady Swaffham, “you’d have to begin by the usual things, I suppose — finding out what the person had been doing, and who’d been to call, and looking for a motive, wouldn’t you?”“Oh, yes,” said Lord Peter, “but most of us have such dozens of motives for murderin’ all sorts of inoffensive people. There’s lots of people I’d like to murder, wouldn’t you?”“Heaps,” said Lady Swaffham.