Is the justice system messed up?
Yes. But the (rightful) lack of conviction and dropping of charges isn't an indication of that. The REST of the justice system is an indication of that.
I don't know if they have it up in Canada, but you can find "The First 48" or "Lockup" online fairly easy. No, they're not necessarily the most representative of murder cases, but from people I know in law enforcement they're pretty damn close to being representative of the kind of murder cases that are seen.
Poor people in America, and in particular poor African Americans in America, don't know jack shit about the legal system. The number of times you see someone ADMIT TO FELONY MURDER and think they're in the clear because they're not the one who pulled the trigger is astonishing. The number of murderers who don't ask for a lawyer, who are just plain dumb enough to talk to the police when they know they've committed a murder and the number of innocent witnesses who ask for a lawyer when all that does is increase the chances of them getting scrutinized for the crime, etc. It's astonishing.
African Americans, yes terribly, live in an environment where their chance of going to prison is insanely high, yet there is little to no understanding of the legal system which puts so many into prison. It's like being a "hobbyist" and not knowing anything about STD transmission or how the birds and the bees work. It must be like living in an electrical power plant and not knowing what electricity is. All you know is that every once in a while someone gets zapped and dies, and the cause-effect relationship is utterly magical.
It's genuinely shocking.
Yes, cops get off on charges a heck of a lot more than Joe Average, the African American. Because they damn well know a little about the law, and they know the system. Can innocent people be charged? Absolutely! And if the accused doesn't know what he or she is doing, they're FUUUUUUUUUUUUUUUCKED. And many, many are, out of pure ignorance of the system in which they live. It's shocking.