In a separate concurring opinion, Chief Justice Harlan F. Stone stated that while he concurred with Justice Douglas's opinion, he believed that, in his opinion, the Act violated Due Process Clause, specifically procedural due process, more than it violated the 14th Amendment. His main argument was that in order for legislation to convict and sterilize the defendant, there needed to be proof that criminal behavior could be inherited genetically, which the court had no proof of at the time. He cited Buck Vs. Bell, saying that because it has been proven that feeblemindedness is inheritable, sterilization is acceptable, but in the case of Skinner vs. Oklahoma, it was not.