Dr. Gordon was the police's initial suspect in the Jigsaw killings. Yet it never occurred to them that these killings took a huge amount of time to plan, setup and execute, so a surgeon who is constantly working doesn't make sense as a suspect. The devices had to be custom built, the killing rooms configured and clues planed and hidden, the victims were under surveillance for weeks. So doing all of this required hundreds of hours. Dr. Gordon is an oncologist and a neurosurgeon, a doctor with dual specialties like this often works 90-100 hours a week easily so most of his whereabouts during the day would have been known by his coworkers. While it's possible that some of the work could have been done at night he certainly wasn't able to survey the victims at night, plus if he was frequently staying up all night to do all of this it would have shown in his surgical skills, his ability to perform surgery would have been severely diminished if he was suffering from sleep deprivation. Dr. Gordon made no sense at all as a suspect, which is something an experienced homicide detective would have realized right away.