Marcetti is a minor character in DEXTER and one of Dexter Morgan's earlier kills (before the current events that started in Season 1). He is featured in a flashback that Dexter has of his first meeting with Rita Bennett.
Marcetti is a man of at least 6 feet in build, somewhat muscular and of hispanic descent. He has slight facial hair that is trimmed to be styled with his short, black hair and wears a dark blue button up long-sleeve shirt with white designs as well as dark (possibly black) dress pants.
Not much can be said for his personality, as he is only a kill that Dexter was focusing on in the past and nothing about what he did is ever revealed. It appears that he's either flirtatious or jokey in nature, as seen while he's talking on the cellphone. He does have some restraint with his anger, not instantly lashing out at Dexter (whom purposely skidded up his car with Marcetti's to get his attention and work as bait) until Dexter grabs him by the throat and injects him with the sedative, to where he tries to defend himself (which ends in failure).
It is unknown what exactly Marcetti did for Dexter to choose him as a target, though it can be assumed he murdered at least one person for no condonable reason and may have even had the potential to kill again.
During a series of flashbacks that Dexter experiences involving his first meeting with Rita in a restraunt, Marcetti can be seen chattering away on a cellphone but is not brought into focus until the end of the first flashback (as Dexter's alternate motive for having this blind date). During the second flashback, Marcetti stands up and leaves the establishment...which forces Dexter to make a quick exit (while apologizing to Rita) and follow him into the parking lot. Dexter had purposely pressed his car against Marcetti's earlier, which would distract him long enough to allow Dexter to make his move. Dexter quickly came up to Marcetti, grabbed his throat and injected him with the sedative...which put him out quickly. The last that is seen of Marcetti is bits and pieces of him in trash bags, with a hand poking out of the top of one of the bags.