The point-blank killing of two New York policemen and protests against the use of excessive force by officers have raised the question of whether people can be prosecuted for words of violence directed at police in social media and on the streets.

Compared with other countries, the United States has a strong guarantee of speech rights even when the words display racism, hatred or violence. State laws, though, generally make it a crime to communicate a specific threat against a police officer or anyone else.

So despite the federal speech guarantees, prosecutors have won convictions for threats against officers.