I've known homeless people and desperate addicts. Many of them would deal in whatever, to feed themselves. That is wildly different from "They would enjoy kill a stranger."

You'd have the accused prove their innocence rather than the state prove their guilt?

No. But I find it strange that people categorically say that a drug dealer never would intentionally kill a buyer. They are violent criminals dealing in poison. They are not perfectly rational businessmen who would never do a thing which could hurt future profits.