CSI: Crime Scene Investigation, Season 9

Gil Grissom:
So, let's assume that 'shoe print' was involved in all four murders. It's possible that he knew, Gerald, right? Is it also possible that he was an accomplice of D.J.K.?

Greg:
That would explain the 9 post-mortem stab wounds in Ian Wallace. It's a continuation of the master's work.

Catherine:
But if he was D.J.K.'s helper, back in the day, why go quiet for 10 years then suddenly start killing again?

Greg:
Maybe he was doing time?

Catherine And when he realized that his old partner turned informant, he got scared and killed him.

Grissom:
Maybe that's what brought the old thrill back. Once these guys get a taste, it never seems to go away.