I think you really need to figure out more specifically what you want to talk about. If you donít narrow your discussion down to a specific concern, youíre going to be drowning in information and things to say.
For instance, are you talking about street crime or war? Do you want to treat a particular problem, gangs in LA for instance, or do you want to talk about the phenomenon in the abstract. Are you proposing a solution or giving a report? Do you want to talk about biological basis, what motivates violence, what the consequences of violence are, perceptions of violence, etc. Each of those topics is rich enough to merit an academic field!
As far as numbers go, consider writing a letter to the public relations offices at the FBI or the Justice Department. These people are often incredibly willing to help and really excited about working with students. When I was in high school, for instance, I did a report on the Chinese occupation of Tibet. I wrote to Amnesty International and The Chinese Consulate in San Francisco and got deluged with information. It made for an interesting report Ė on one hand I had a horrific list of atrocities and human rights violations, and on the other I had reports on the number of miles of road laid, improvements in the literacy rate / health, etc. since the take over.