Can I tip off police to search someone's home for illegal (date rape) drugs

Location: Washington State, USA

I believe a young woman I know (we'll call her Lisa) got roofied and raped by a "friend" of hers when she was staying over at his home. She says that he gave her a pill "for cold sores," and it made her too tired to fight him off. I don't know much about drugs, and I assume she could've been made sleepy with OTC's as well, so I understand that a police search might find nothing illegal. But is there a way to do that, without getting Lisa involved? She never reported the rape because she didn't want to do the trial. It has been a few years since it happened.

I'm just wondering if I can prevent him from doing it to someone else.