Murderabilia – Serial Killer – Dennis Rader (b.1945) Personal Calculator – the personal calculator with ‘Rader’ scratched to the top, with a Kansas Department of Corrections Inmate Property Receipt signed by Rader dated 2013, plus a signed photograph from Rader inscribed ‘The Mad-Non-Hatter’ dated 2014 and signed and inscribed the same on the reverse of the print (3) Note: Dennis Lynn Rader (b.1952) is an American serial killer who murdered 10 people between 1974 and 1991. Know as the ‘BTK Killer’ or the ‘BTK Strangler’, ‘BTK’ stands for ‘Blind, Torture, Kill’, which was his infamous signature. Currently serving 10 consecutive life sentences in Kansas.