If there's a better approach to reducing murders by psychopaths than decreasing the number of psychopaths (by hindering them from reproducing), I'd opt for that.

I feel I should point out that the harms of psychopathy are only rarely covered by murder.

(eg. Cleckley in The Mask of Sanity places great and repeated emphasis on how almost none of his patients ever engaged in violence worse than beating their wife, and I don't think he mentions any murders ever, even though the case studies are otherwise a long litany of constant crime, deceit, fraud, and destruction (including a truly astonishing amount of forgery of checks).)