Replace the word "good" with "competent" if you'd like (I'd prefer "sleazy").
Why would any defense lawyer posit such a deal unless he presumes his client's guilt--
"Gee, Mr Westerfield, we got you life in prison just as long as you lead investigators to the body. Now we know, of course, that you weren't connected to the crime, and don't know where the body is, so we've contacted a psychic who's had very good success located missing persons....