Do priests hearing confession have an obligation to report serious crimes?

Attorney client privilege in California is as strong for confession of past crimes. Future crimes must be turned in. There was a case a year or two ago where a lawyer had heard a confession from his client where another man was serving a life sentence for the crime. Only many years after the client died had he been allowed by the client to tell.

That exemption intrigues me. Do you have any insight into the rationale behind it?

The plot premise of Hitchcock’s I Confess turns on this inviolability of the confessional.

I imagine it’s to guard against what would otherwise be a temptation for a priest to ease his way into an affair by assuring his partner that even if they did commit adultery, he could absolve her of the sin.