That's part of the point, how the hell after a year of investigating, can the police have no credible leads?
How is this part of the point? You and other posters were trying to make this a media/race issue, but it's also an issue of how police don't try to solve murders of white women? If she was black, the case would be solved by now?
My guess is the police have rounded up the 17 best Gangster Disciple earners in that area and taken them off the street to cut into their cash flow. Someone will either talk, or end up dead, then back to business as usual.
The police aren't even trying to connect the 17 arrests to solving Jessica Chambers' murder. They actually said that it's unlikely the arrests will result in solving the case. The only thing connecting the arrests to her murder is that following her murder, they cracked down on gang activity. That's it.