WHEN THE district attorney and the police commissioner held a news conference last week about the Philly teen who says he was abused by cops, I figured that was that.

Police would say they investigated as best they could, given the lack of cooperation, but found no evidence of wrongdoing. Blah, blah. Case closed.

Instead, Commissioner Charles Ramsey and D.A. Seth Williams announced a joint investigation into 16-year-old Darrin Manning's allegations of police brutality.

Well, I'll be . . .

"We don't normally confirm ongoing investigations, but given the nature of this case, we felt it was important to let the public know that we have been vigorously investigating this case since it occurred," Williams said.

One problem, the visibly grumpy duo said: No one is talking.

Not Darrin Manning, who said he was stopped on Girard Avenue near Broad Street on Jan. 7 while on his way to a basketball game and then assaulted by a female officer who ruptured his testicle. Manning's lawyer, Lewis Small, had said he wouldn't allow Manning to speak to police unless charges for simple assault, resisting arrest and reckless endangerment were dropped.

Not teammates, who were with Manning when a police officer stopped them for wearing ski masks and running off. The cop also said that Manning assaulted him during the arrest. Manning denies striking the officer, and he and teammates said they weren't wearing ski masks, just hats and scarves given to them by a school administrator on a record-cold day.

Not even the seemingly clear-eyed bystanders - who told me that, from their vantage point, cops used excessive force - are stepping up. They said they feared getting involved.

"Nothing gets resolved if you don't talk," Ramsey told reporters Thursday. "I've been here six years and I think I've demonstrated that I will take action against a police officer who acts inappropriately . . . but I can't do anything if I don't have people come forward and speak."

I haven't been in Philly as long as Ramsey, but even I know that the chasm between many of Philadelphia's citizens and police runs deep. Why do you think this case has resonated the way it has? It speaks to longstanding mistrust and disrespect - on both sides.

I still can't wrap my head around how police and city brass skipped a community meeting following the incident. More than 100 residents gathered at a church on a frigid Friday night to discuss the case and to improve relationships with police. They deserved to be heard, and acknowledged.

But that moment's passed. Right now, we have a teenager with no prior record whose injury might prevent him from fathering children, a video shot by a rotating camera that only partially shows what happened and a bunch of bystanders and witnesses who aren't talking. And we're expecting what, exactly?

After the announcement of the joint investigation, Manning's attorney told reporters that the teen will meet with authorities soon. Great, but without more people stepping forward to say what they saw, that could add up to one big "he said, they said." How do you think that's going to play out?

Will people speaking up guarantee that Manning's allegations will lead to the officers' discipline or dismissal? Nope. Even when cases seem like slam dunks - remember the veteran lieutenant caught on video cold-cocking a woman at a 2012 Puerto Rican Day celebration? - too many misbehaving Philly cops seem to be made of Teflon. After being fired by Ramsey, that cop got his job back in arbitration.

So yes, I get why people might think there's no winning against the blue wall of untouchables. But the D.A. and the police commissioner seem to be taking Manning's case seriously enough to plead with the public to come forward - twice now for Ramsey.

We can use this case to highlight issues of race and racial profiling - Manning is black, the officer who stopped him is white. Police have refused to identify the female officer. We can, and should, use it to debate stop-and-frisk practices and the broken relationships between citizens and the cops charged to protect and serve them. But if we don't do our part, right here and right now, what we're going to do is make it a hell of a lot easier for potentially bad cops to walk.

Williams said he intends to wrap up the investigation before Manning is due in court next month. He said anyone with information about the incident may contact his office at 215-686-8000 or via email at justice@phila.gov.

"At this point, we have no basis to believe that a police officer did anything wrong," he said.

And maybe they didn't. But if you saw differently, the time to step up is now. Right now.

Phone: 215-854-5943

On Twitter: @NotesFromHel