Most serial killers are chilling.
I only worked with one and he could pass any lie detector test because according to him, he didn't do anything wrong.
Look at Peter Tobin. It's likely he's the Bible John killer.
But keeping his silence is a means to still exert control.
He's still horribly violent, even in his 60s, in prison. He's been involved in several violent affrays and survived at least two attempts on his life by other inmates.
He only stopped appealing because of the actions of the fathers of two of his known victims, Vicky Hamilton and Dinah McNichol, both their mothers drank themselves into early graves, consumed with grief over their missing daughters, whose bodies were only discovered long after their deaths. These fathers were instrumental in changing legislation for appeals for people convicted of murdering 3 or more persons.
He still has not breathed a word about their murders, of which he's been convicted, or that of Angelika Kluk, a Polish immigrant to Scotland, whose raped, mutilated body was found in a church in Glasgow. Tobin was in his 60s at the time of her murder.
Before the new legislation, he launched three appeals for which he failed to appear, from prison, each costing the taxpayer over £100,000 for which Mr McNichol had travelled from England to be present for.