No, it's from Criminal's Education 101. You can be sure criminals know exactly the punishment for their crime. Even petty theives know the line between misdemeanor and felony and avoid it carefully. Kidnappers know when it becomes capital, robbers know when it becomes capital - and all but the most inept do whatever they can to avoid capture and conviction.
If there is no penalty, only potential benefit, from killing the victim, criminals will very likely escalate the rape to murder.
I do not agree with Criminal Education 101. That uncivilized creature that kidnapped those two girls seems well schooled in Criminal Education 101. These freaks are running the criminal justice system.
I still say "poppycock".