Over the past few years the United States of America has become embroiled in controversy over the issue of racially-charged police brutality.
A series of well publicized shootings of unarmed African-Americans by law enforcement, done with apparent legal impunity, have prompted protests across the nation.
Entities like the Black Lives Matter movement have argued that race-based police brutality is a pervasive problem throughout American law enforcement.
Others, including conservatives and assorted police unions, have argued that the killings of unarmed black men are often taken out of context or are isolated incidents.
Below are four analyses made by different researchers over the past year that have drawn varied conclusions when looking at the data.