I don’t know. Maybe it’s like Law & Order Criminal Intent where 90% of the perps are white males and the other 10% are white females.
The only time I saw someone that was black accused (Whoopie Goldberg), she, in the end, outsmarted the white man and we never saw what happened unless there was a sequel.
Not that they aren’t biased or anything.
That happens with successful shows. X-Files another example.