You can't find the study because it doesn't exist. In the United States and in the UK there is a huge disparity in violent crimes committed by race.
http://m.huffpost.com/us/entry/8078586.html - 1) If a black person and a white person each commit a crime, the black person is more likely to be arrested. This is due in part to the fact that black people are more heavily policed.
http://blogs.channel4.com/factcheck/factcheck-black-american...