" It’s a lot harder to access serial killers for interviews than it used to be. Even for interviews that are strictly law enforcement related, the days of simply showing up at a prison and presenting your credentials as Bob Ressler and I used to do are long gone. Not only does the inmate have to give informed consent, but there are so many rules relating to safety, criminal process, and correctional system bureaucracy that getting in to see violent offenders is extremely difficult. "

― John E. Douglas , The Killer Across the Table: Unlocking the Secrets of Serial Killers and Predators with the FBI's Original Mindhunter