On March 19, 1999, Dupas posed as a potential client and visited Patterson at her Northcote home, which also housed her psychiatric office, for a scheduled appontment. He instead killed the woman, stabbing her 27 times. Arrested and convicted in the Patterson killing, Dupas was sentenced to life imprisoment with no possiblility of parole. Justice Frank Vincent addressed Dupas saying, "I doubt you are capable of remorse", and assessing the chances of rehabilitation stated they were "so close to hopeless they can effectively be dismissed."

Dupas is a major suspect in several other Melbourne killings including the murder of Mersina Halvagis, who was stabbed to death while visiting her grandmother's grave. Margaret Maher, who was also stabbed to death in October of 1997, is also a likely victim. Another strong possibility is the murder of Helen McMahon in February of 1983, which took place in almost the exact same spot that Dupas had previously raped another woman just weeks prior.

10/2/2002-Dupas has been formally charged in the murder of Margaret Maher. DNA evidence has linked him to Maher's slaying.