As he had with Hindley, Brady began to introduce Smith to his perverse philosophy - lending him books on De Sade and the Nazis as a precursor to bringing him inside the circle of horror he shared with Hindley.
At their late night drinking sessions, Brady told Smith about the murders he had committed, but Smith remained outwardly neutral and - he claimed - inwardly sceptical. Brady, perhaps detecting Smith's doubt, picked up a 17 year lad and invited him back to the house he shared with Hindley at Wardle Brook avenue.
With the boy sitting on Brady's sofa, unaware of his impending fate, Hindley fetched David Smith over to the house. When Smith arrived, he entered the room just at the moment that Brady launched his deadly assault. With what was estimated to be fourteen blows of a heavy axe, he murdered Evans in front of the terrified Smith - finishing the job with a ligature around his neck.
Satisfied with his work, Brady sat down as Hindley fetched a cup of tea prior to the clean up operation. Scared for his own life, Smith found himself helping the pair parcel the body up and mop the floor clean of blood.
Eventually, he left the house and went to bed with his wife. Unable to sleep, he blurted his story to her in the middle of the night and the first thing in the morning she persuaded him to walk to a nearby phone box to call the police.