Peter Manuel's crimes were motivated by more than just the need for money. While material gain played a role in many of his offenses, the sources highlight additional driving forces behind his actions

From his early attacks on women in Mount Vernon to the murder of Anne Kneilands, Manuel's crimes frequently had a sexual element. Manuel seemed to derive excitement from the danger and risk associated with his crimes. This is evident in his assault on Mary McLachlan, where he was aroused by the thrill of almost being caught. It's also apparent in his enjoyment of taunting the police and his decision to represent himself in court.

His actions were frequently impulsive and difficult to rationalize, stemming from a combination of his troubled upbringing, lack of remorse, and inflated ego. While financial gain was a factor, it was often overshadowed by Manuel's darker impulses, making him a particularly chilling figure in the annals of criminal history.