By the time Liz Garbus’s two-part documentary “Who Killed Garrett Phillips?” debuts on HBO, there could be a new public lead in the case of the murdered titular 12-year-old. As least, that’s what many may hope after the new St. Lawrence County district attorney admitted a new tip earlier this spring. Garbus says she would do a follow-up to her doc if need be, but she admits that after her experience getting to know the Potsdam police for the project, she doesn’t think it’s likely.

“The chief of police is now Mark Murray, who was the lead detective on the case. He thought Nick [Hillary] was the guy, so I think the likelihood of this being pursued by the police — and the DA needs the police to do the pursuing — is pretty low. But I hope I’m wrong about that,” Garbus tells Variety.

Over four hours, Garbus’s “Who Killed Garrett Phillips?” painstakingly covers the surprising murder that rocked the small town in Northern New York in 2011. Starting with talking heads with the neighbors who first called 9-1-1 after hearing a crash and ominous moaning coming from inside the Phillips’ apartment, Garbus takes her audience back to Phillips’ last moments and then expands the story to include similar interviews with police and journalists alike who investigated the crime, as well as the former district attorney who pushed for an arrest, Phillips’ uncle Brian, and the man who stood trial for the crime (Hillary).

After first reading about the case in a New York Times article, Garbus recalls being struck by the “thematic issues and concerns that, I think, are ones that spoke to larger systemic problems.” Specifically what caught her attention was that the local police’s focus was on one of Phillips’ mother’s ex-boyfriends, a Jamaican American man who was well-known around town as a soccer coach, despite the fact that he had an alibi and that there had been rumblings of other possible suspects early on.

“We did hear these rumors, and we wanted, as much as we could, to go out and explore them and accompany local journalists,” Garbus says, “but there really was so little [to go on]. There was really nothing beyond what’s in the film that we were able to learn.”

Murray and another officer, Gary Snell (who Garbus notes declined to be interviewed for the doc), interrogated Hillary after conducting a joint interview with Phillips’ mother Tandy and John Jones, who was not only her ex-boyfriend but also a sheriff’s deputy at the time of the crime, and later briefly brought under suspicion because he was seen on tape by Phillips just before the murder.

Garbus says her team did “analysis on that tape beyond what the police had done” but no new developments came out of it.

“From the police’s point of view, they thought they had the best suspect — the most they could put together on someone,” says Garbus. “But you can’t take race out of the picture — the way in which white Americans are just more likely to look at Black people as capable of committing crimes. The issues around race and policing and prosecutorial misconduct have been huge issues across our nation. And that was the tunnel vision.”

And that was on what Garbus wanted to shine a larger light with this project. After all, she notes, “the ‘Justice for Garrett’ campaign became ‘Get Nick Hillary.’ They were always, always intertwined. There was very little energy around anything else in this case.”

Over time, as Garbus kept asking the key players in the case to relive and rehash the nitty, gritty details, she says she doesn’t feel that changed. While there would be the occasional “inconsistency” in a detail someone’s story, be it Hillary’s or Murray’s or Jones’s’ — which she didn’t shy away from including in the final cut — everyone was adamant about their beliefs. Hillary still swears by his innocence, while the cops and prosecutor reiterate that Hillary “was the only person who could have done this and had opportunity in their minds.”

That’s why “Who Killed Garrett Phillips?” devotes so much time to following Hillary himself. Garbus and her crew interviewed him many times, filmed him with his kids and in his home, and included footage of his 2016 trial.

“The Phillipps family was victims of prosecutorial misconduct, as well as Nick,” says Garbus. “The original DA did not feel that she could mount a case, and Mary Rain mounting the case put them through an enormous amount of hope, and then disappointment.”

Rain ran for district attorney of Potsdam in 2013 with a platform that specifically singled out Tandy Phillips, promising to prosecute someone for the murder of Garrett. This led to Hillary’s arrest, which satisfied Brian Phillips, who still passionately professes his belief that Hillary is guilty in Garbus’ doc. Whether Phillips’ mother agrees remains to be seen. Garbus shares that she was in contact with Tandy while in production on the project, and she expressed the possibility of sitting down for an interview once the trial was over. But the verdict came down as not guilty, and Tandy never ended up going on the record with Garbus.

“Whatever you might say about the film and how it portrays the justice system and Nick Hillary, my hope is that it also reflects the pain of the loss of this family and the gaping hole it left in their lives,” Garbus says.

With the case still very much open and unsolved, justice for Phillips has not been achieved. Garbus credits the “dogged” local reporters who wouldn’t let up on the case for bringing it to the larger attention, including her own. “They are the only reason that Nick is not in prison,” she says.

Now, she hopes her doc will put similar pressure on the story so that maybe her titular question can finally be answered.

“True crime is popular because there’s a healthy impulse to want these things to be solved,” Garbus says. “Tips come in. People want to be heroes. I think of Michelle McNamara: Did that book [‘I’ll Be Gone in the Dark’] solve that case? No, the police did. But at the same time, so many armchair sleuths, so many Reddit boards, so much discussion only increased the chances of it being solved.”

“Who Killed Garrett Phillips?” airs July 23 and 24 on HBO.