That's an interesting story. And I wonder if to some extent the creators of "Proven Innocent" drew from his experience. Though the heroine of the show was able to get her conviction overturned, which made it possible for her to take the bar exam and take on court cases. Reilly really did commit the murder he was accused of, and admitted to it.
Undoubtedly Reilly is right when he says that statistically, murderers are less likely than criminals convicted of other crimes to do it again. That makes sense, unless we were talking about serial killers, but they don't get released.
Though I've read a lot of true crime books, I've never really studied the subject. But I think most people who commit murder do so either as an impulsive act--they're drunk or on drugs, and lose control--or because they have, or imagine they have, a real grievance against the victim. If the latter, they're unlikely to do it again, because they have, ah, eliminated the problem. If the former, probably they learn better impulse control as they get older. Generally speaking, most violent men are younger than 35.
Other murderers, whether men or women, are psychopaths who kill either because it's a sexual thing or--in the case of most women serial killers--simply because they feel the victims stand in the way of something they want. For those people, it's not personal.