There is one simple reason. There is one solution that I can suggest.
The reason is simple. Black gang memebers are killing other black gang members and accidental bystanders. No black citizens are willing to identify the killers because they themselves will be killed.
No witnesses, no success in taking killers off the street.
My solution is to allow video testimony in court if the witness is killed before the trial.
The TV testimony would have to include cross examination in order to meet the requirements of the fifth amendment to our Constitution.
The Constitution did not consider the problem of gangs killing witnesses. Juries should also be informed before the video that the witness was killed before the trial.
This proposal will not initially be welcomed by witnesses. But over time as its effectiveness becomes obvious and well known it should result in a dramatic increase in the number of witnesses and the decline in black homicide.
It may work where witness protection programs don't. Witness protection is generally nonsense because few ordinary people want to start a new anonymous life.