Mac keeps a pile of unsolved cases on the corner of his desk. Rapist/murderer DJ Pratt's file remained there for some time, until the CSIs closed it with the posthumous assistance of former colleague Aiden Burn. Mac says the pile used to be bigger, which helps validate his feelings about being a CSI. He usually sacrifices his off-days when cracking a cold case or an urgent case (episode 3.16 "Heart of Glass"). Flack commented in episode 5.23 "Greater Good" that Mac "must've been the kid who did all the extra credit questions and made us all look bad" after seeing him at work on an off day. In episode 1.01 "Blink" Stella expressed her concern about Mac after finding out that he skipped his off hours and dived right into the new murder case.