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Inverted in the Discworld book Jingo. After an assassination attempt on a major Klatchian official, Commander Vimes of the Watch immediately suspects everybody except the Klatchians, who turn out to be behind the murder attempt after all.
Coalface in Men at Arms is the Fantastic Racism counterpart; a dwarf was killed, he's a troll, as far as Mayonnaise Quirke of the Day Watch is concerned, you don't need any more evidence than that.
Although Tom is a very nice man who isn't scary in the least, and of course, is completely innocent. However, most of Maycomb assume he is a scary minority suspect who did rape Mayella because of the prevailing racist attitudes of the time.
Mocked on The Wire. When a white man is giving a discription of OmarLittle to Bunk, he describes Omar as huge and so is his gun. Bunk and another black detective share a chuckle over their in-joke: BNBG - Big Negro, Big Gun.
Subverted in one episode of CSI. While the Scary Black Man the CSIs first suspect didn't actually kill the murder victim (the murder was actually done by the white pedophile who offered his services as a "consultant" to Grissom), he did viciously beat the victim and his friend while he was babysitting them, which made them run out of the house until they were picked up by the real killer. He's arrested on assault and battery charges, and it's noted that, even if he didn't kill the boys himself, he indirectly contributed to their deaths.
Patrice O'Neal has a bit where he discusses how this trope makes him afraid when a white woman walks by him:
Oh Jesus, I hope nobody kills this white woman because I'ma get blamed for it.