"I expected something to happen," said Linden Wagner, who wrote the poem that he and his accomplices chanted after he assaulted and set alight his friend Kirsty Theologo, 18, and throttled her 14-year-old friend.
"In American films, people who sold their souls died physically and then came back to life," he said.
On Wednesday, Wagner testified that he had wanted to sell his soul so he could gain power.
"When you sell your soul, you gain something. You can gain money, power and fame," he said.
The attack on Theologo and her friend occurred at a hill in Linmeyer, in Johannesburg south, in October 2011.
Theologo died of her injuries a week later, but her friend survived.
Wagner, Courtney Daniels, Harvey Isha, and Robin Harwood are currently on trial for the murder and attempted murder. All have pleaded not guilty.
Two other accused, Jeremy King and Lester Moody, confessed to the crime and were each sentenced to 17 years' imprisonment, five of them suspended.