Damien Echols (Jeff Dailey/Sony Pictures Classics)

West of Memphis is a triumphant story of justice finally prevailing for three innocent men who spent 18 years in jail for the gruesome 1993 murders of three eight-year-old boys in West Memphis, Arkansas. Or, it’s a story of how celebrities with deep pockets can be inspired by a scrappy HBO documentary, and the grassroots support it generates, to pay for expensive forensic analysis and legal representation as well as commission a documentary to follow and extol their efforts to win the release of Damien Echols, Jason Baldwin, and Jessie Misskelley, Jr. in 2011.

Uncomfortably touted as “the untold story,” this deliberative version builds on Joe Berlinger and Bruce Sinofsky’s groundbreaking investigative Paradise Lost documentaries (and includes some of their clips as well as the usual TV news clips). It was made almost simultaneously as Berlinger and Sinofsky produced the finale of their trilogy, Purgatory (2011). It was their Paradise Lost: The Child Murders at Robin Hood Hills (1996) and the second Revelations (2000) that inspired The Lord of the Rings’ Peter Jackson and Fran Walsh in 2005 to bankroll the expensive forensic research and legal teams that eventually accomplished the three men’s release, and lead to this documentary about Jackson and Walsh’s private investigation. It’s director Amy Berg’s first feature since her trailblazing Deliver Us From Evil (2006).

The original team focused on the hysterical wave of shockingly trumped-up anti-Satanism that swept over the small-town community, and which turned the atmosphere into something like the Salem witch trials. The defendants’ fondness for heavy metal music both separated them from the rest of the town and gained them international grassroots support that kept their cause alive for more than 18 years. One advocate was New Yorker Lorri Davis, who married Echols while he was on Death Row. Both are producers of this film.

While both this film and the trilogy spend considerable time pointing fingers at other possible suspects, who are related to the victims, this film is quite suspenseful when it’s straightforward—the best CSI investigation that money can buy. (Incidentally, both sets of filmmakers provided payments to the victims’ families to participate.)

Berg begins simply enough by tracing the boys’ movements on their last day—and it turns out that the police, in fact, did not do the same, nor did they check the alibis of people who were reported seen with them or interview other possible suspects. But even with the same unqualified consultants, local law enforcement officials, and prosecutors on camera here, too, it is still baffling how the opinions of a couple of zealots, who imagined local Satanists and cultists meeting in the woods, could set off this legal maelstrom, including pressing one of the then-teenage defendants into a false confession. (The issue of false confessions was dealt with much more clarity in Grover Babcock and Blue Hadaegh’s 2011 documentary Scenes of a Crime.)

Berg carefully shows how the forensic investigation was not based on facts. The most inflammatory evidence of the cruel desecration of the bodies is rationally shown here to have been caused by biting turtles native to the waters where the victims were found. There’s also a lengthy consideration of what knife did or did not do the deed, let alone possible traces of DNA, that goes off in confusing directions. While the forensic experts are apoplectic at the poor quality of the consideration of the physical evidence, the low standards of local medical examiners in general have already been the focus of investigations by PBS’s Frontline.

Where one of the earlier films honed in on jury manipulation, this one, though, finds a witness who tearfully recants her testimony. While celebrities (Eddie Vedder, Patti Smith, Johnny Depp, Natalie Maines) explain why they raised money and helped keep the plight of the jailed “West Memphis Three” in the public eye, it’s a bit awkward that producer Jackson narrates on camera key elements in the case rather than featuring a technical expert.

Both films have the same footage from the Arkansas Supreme Court argument that the new evidence justified a new local hearing, which eventually led to the complicated legal gymnastics that finally got the three men freed. This documentary has the satisfying benefit of being able to follow-up with each of the former defendants since their release, particularly with Echols, allowing the audience to see how they aged, let alone sustained themselves, while waiting for far too delayed justice.