CSI: Miami is bringing back Rory Cochrane who played Tim Speedle on the show until his character was killed during a gun malfunction in 2004.
CBS isn't saying HOW he's coming back but it isn't a flashback. This E! article has some suggestions: "There's no word as to how Jerry Bruckheimer's minions are going to explain Speedle's resurrection, but you've got your faking death, your witness protection, your evil schemes…etc."
Welcome back Rory, watch out you don't get hit with Caruso's aviators as he whips them off to talk to you!