Comey used a speech at Georgetown University to offer his most expansive take on a debate that has roiled in the country in recent months about police use of force and interactions with minority communities.
The deaths at the hands of white police officers of Michael Brown in Missouri and Eric Garner in New York, as well as the more recent slayings of two New York police officers, have raised difficult issues on both sides of the debate, he said.
"The two young black men on one side of the street look like so many others the officer has locked up," Comey said.
"Two young white men on the other side of the street even in the same clothes do not. The officer does not make the same sinister association about the two white guys, whether that officer is white or black."
Comey joined Attorney General Eric Holder in calling for better data about how often police use force. Such information is needed to make sound policy decisions, Comey said.