A spate of shootings in New Haven in the last week resulted in at least three casualties, bringing the total number of New Haven homicides in 2008 to 18 — five more than last year. Last Friday, a victim was brought to the Hospital of Saint Raphael with a gunshot wound to the head and later died on Tuesday. Early Saturday, city officers responded to a scene on reports of shooting at 95 Kensington St. and found a man, who was pronounced dead at the scene, with multiple gunshot wounds. On Monday, a New Haven man was shot in the chest near Exchange and Lloyd streets. He died Tuesday.