He was a wedding photographer, who killed young women.
Phillip Barnes worked as a wedding photographer for many years and had a wife named Patricia, and a son named Tyler. According to Tyler, Phillip beat him and his mother regularly whenever he was home. When he worked, Phillip would find a young woman guest from out of town. He'd spend money and charm her into coming back to his hotel room so that he could kill her. He took pictures of what he did and kept them as trophies.
One day, Dexter Morgan noticed this pattern of disappearances and tracked Barnes down. On 19 May 2007, Dexter followed him to an out of town job and picked him up after a wedding reception (where unknown to Dexter, his own picture was taken). Dexter then collected a blood slide from Phillip and killed him.
The disappearance of Phillip was later investigated by Captain Maria LaGuerta and Lieutenant Debra Morgan in connection to the reopening of the Bay Harbor Butcher Case. Captain LaGuerta tried to find evidence of the Butcher's identity but was stopped by Lieutenant Morgan when she hid a photo of Dexter at the wedding reception. Debra later gave it to Dexter who destroyed it.