I haven't watched "48 Hours" (if you mean the CBS show), but "The First 48" on A&E matches your description (as well?) and is one of my favorite shows.
Sometimes I worry about an analog to the "CSI effect"--a number of things go by that name, but here I mean an inadvertent way of teaching aspiring criminals how to conceal their crimes (in the case of CSI, primarily forensically). Occasionally suspects who appear on "The First 48" (as the camera follows them after their arrests) shout out something about having watched it.
Then again, I suspect that the number of stupid murderers will be nice and steady. It also doesn't hurt that many murders on the show appear to be drug-related.
yeah, I meant “The First 48”.
Oh, and yeah, the smart criminals probably do learn a lot of forensics from the various crime shows, but fortunately the bulk of criminals can’t even write their own name, so not to worry too much about piddling anti-crime-detecting lessons like the trackability of moving cell phones, etc.