Official proof that something/someone is of boner producing quality. "hard evidence" must be confirmed by at least two people to constitute its legitimacy.
"I'm pretty sure Mrs. Moses just licked her lips and moaned at me, I have some hard evidence to back that claim up."
"AJ, the grammar police are here. They want to speak to you about your run-on sentences. One of them is a sexy female cop. You can tell because of my hard evidence."