It is disputed if John Wayne Gacy was dressed as a clown when he killed his victims, but like all funnymen he always had a trick or two up his sleeve. But, unlike most clowns, the former KFC manager also known as Pogo's pranks were used to kill.
One involved tightening a rope with a hammer handle, throttling his victim, the other involved a pair handcuffs.
In this archive footage, Gacy jovially demonstrates to a naïve TV reporter "how to tie knots" - giving a glimpse of how he was able to snare so many innocent men in a similar way.
As the newsman passes him a shoelace, Gacy grins, "Shoelace? You’re in trouble now? Aren’t you scared sitting that close to me?"
He then explains that "you don’t need it this long", and that he would use the rosary given to him as a child to throttle the unlucky young men who had crossed in to his path.
Gacy smiles: "I had a rosary that I carried in my pocket, I’ve always carried a rosary, it was my communion rosary."
He then appears to imply that he creates a scenario where his victims ask him about certain types of knot - which he would reply he only knew tourniquet ones, taught to him when he was in the Boy Scouts.
Taking the wrist of the unknown reporter, he then demonstrates the double knot, using a biro to twist the string tighter and tighter with minimal effort.
He says: “OK here's what I told him, sit here, all you do is you wrap it around you put one knot in it, and I said then you put a second knot in it okay. I said then you take a stick and stick it in here and you just turn this and I says because this is a tourniquet I said that's the only knot I ever learned.”
Chillingly, it is the same knot found wrapped around the necks of his victims in the crawlspace beneath 8213 West Summerdale Avenue, Gacy's home up until the time of his arrest.