A group of 20 Miami police officers fired nearly half of all the bullets expended by the 1,100-officer department since 1990, making them some of the most aggressive shooters in the nation, a Herald investigation has found. The group includes seven officers now under indictment on charges of planting guns at police shooting scenes and four who have been disciplined for lying to supervisors in unrelated cases. One officer - Juan Mendez - has accumulated four fatal shootings, more than any other police officer in Florida, according to a Herald survey of more than 25 urban police departments in Florida and the nation. "Make sure when you're telling people I'm Florida's deadliest cop that you also tell them I'm working in Florida's deadliest city, on Florida's deadliest streets, and on Florida's deadliest shifts, " Mendez said in a recent interview. "I do not go out there looking to shoot people." Miami Chief Raul Martinez acknowledged that the problem of repeat shooters is particularly vexing - especially when there is no clear evidence that the shootings were unjustified. "It's one thing when officers fabricate evidence, plant guns and tell lies, " Martinez said. "But what happens when you appear to have good, justifiable shootings, . . . when they say I had to shoot to defend myself? "It's difficult to tell them when not to shoot." Police have grappled with the question for years: Are some officers more prone to shoot because of their mind-set and tactics, while other officers might avoid shooting? In Mendez's case, for instance, the suspects were armed in three of his four fatal shootings and the cases were ruled justified by the department. Yet his commanders acknowledge they will never know whether another officer - one of the more than 900 who have never fired their weapons - might have avoided deadly force. "If there is one thing that has failed us, it's that, " Martinez said. "Once you have an officer who's involved in three, four, five, six justifiable shootings, what should we do with him? We haven't found the answer." A yearlong Herald review of every bullet fired by the department revealed failed oversight in 46 questionable police shootings throughout the 1990s, many of them involving the department's most aggressive shooters. Mendez, who was involved in one of those questionable shootings, is among six Miami officers with more than five shootings in their careers, a number higher than almost all other urban departments surveyed by The Herald. Many - including Baltimore, Boston, Chicago and Philadelphia - reported that they have no officers with that many shootings.

COMPARING SHOOTINGS Other, larger forces show a better profile than Miami

Miami-Dade County's police force, with three times as many officers, has none with that many either. Tampa police, with nearly 1,000 officers, have one officer with four shootings and one with five. Washington, D.C., with nearly 3,500 officers, reported only one officer with more than five shootings. Even New York City - with nearly 40 times more officers than Miami - reported only seven officers with five or more shootings. "That's incredible, " said Bishop Victor T. Curry, a longtime black community activist and frequent critic of the Miami police. "It's clear they would rather suffer with the reputation that they employ a bunch of Keystone Cops than to cut out this cancer and move on." But the officers and their supporters argue that they are being unfairly labeled as bad cops. "What we're dealing with here is a select group of people" put into specialized units and "tasked with finding violent felony offenders, " said Al Cotera, head of the Miami police union. Supporters say shooting statistics should be stacked alongside commendations and arrest records, and that their honed skills as alert, aggressive police officers put them in harm's way more often. "I notice things - what am I supposed to do?" Officer Mendez said. "Why? I don't know why. Why does Barry Bonds hit more home runs?"