On May 6 1993, the mutilated bodies of three eight-year-old boys were found in a woodland area known as Robin Hood Hills in the town of West Memphis in Arkansas. The discovery sent shock waves throughout the local community – parents were frightened to let their children out unaccompanied, and the pressure was on the authorities to find the killer or killers as fast as humanly possible. The very next day police were interviewing possible suspects, and less than a month later they announced that they had arrested 17-year-old Jessie Misskelley, 16-year-old Jason Baldwin and 18-year-old Damien Echols, the claim being that the three had murdered the boys as part of a satanic ritual.

Enter filmmakers Joe Berlinger and Bruce Sinofsky, fresh from the acclaim for their first documentary feature, Brother's Keeper, with a commission from HBO to document the case and the subsequent trial. Berlinger and Sinofsky freely confess that they initially believed that the boys were guilty and that they would be making "a real-life River's Edge." But as the trial progressed it became clear that the case against the three was full of alarming holes, and that the boys were in danger of being convicted not on hard evidence, but because they were perceived as different. 150 hours of footage and a year of editing later, the finished film was screened to widespread acclaim, won a number of prestigious awards, and in time became the rallying cry for a support group campaigning for the release of what became known as the West Memphis Three.

Though the film effectively highlights what the makers came to firmly believe was a woeful miscarriage of justice, those expecting a polemic in the style of Michael Moore are in for a surprise – Berlinger and Sinofsky's approach is remarkably even-handed, giving equal screen time to both sides of the case and never for a moment allowing us to forget the truly horrible nature of the killings and its effect on the families of the murdered children. This is established from the off in the sometimes graphic extracts from the police crime scene video that make up the opening sequence and is carried through in sympathetic interviews with the distraught families of the victims.

Viewed in retrospect, the access granted to the filmmakers here is little short of astonishing. Covering the trial itself with multiple cameras, they were also allowed to record the strategy meetings of both the prosecution and the defence councils, as well as sessions with their clients, to a degree that later dismayed members of he legal profession and simply would not be permitted today. Berlinger and Sinofsky also befriended the families of both the victims and the defendants, resulting in some extraordinarily frank and intimate interviews, some of which are genuinely upsetting to watch. And so they should be. As things progressed, the idea of making a real-life River's Edge gave way to a determination to record the impact of this tragedy on the inhabitants of the small American town in which the crime was committed, with the focus then shifting again to include an examination of the damaging effects of prejudice on justice.

If this level of access and the non-partisan approach were not remarkable enough, we have the trial itself. Initially, there's a sense is that this is all cut and dried, with Damien and Jason implicated by a confession from Jessie. But there are problems here, as despite being 17 years of age at the time of the arrest, Jessie has an IQ of just 72, and it becomes clear that the confession was at least partly the result of police badgering and coercion. It also emerges that there is no actual evidence linking any of the suspects to the murders, and that the entire case against Damien and Jason centres on the suggestion that they killed the boys as part of a satanic ritual. The evidence for this? Well, Damien dresses in black, listens to Metallica, reads Stephen King novels, and is aware of the work of Alistair Crowley. In the eyes of this deeply religious and traditionalist community, this marks him as a freak and an outsider, and probably capable of just about anything.

As the trial progresses, the flaws in the prosecution case start to pile up – the lack of blood at the crime scene, the impossibility of inflicting a precision mutilation in the dark, the complete absence of mosquito bites on any of the suspects when the murder site was infested with these insects. Even council jaws drop when it is revealed that a blood-soaked suspect was not investigated in any detail, and that there was no test done on his blood because the only sample taken was lost by the testifying officer. But even as the prosecution case begins to resemble a Salem witch trial, Berlinger and Sinofsky maintain an extraordinary level of balance, with Damien in particular emerging as his own worst enemy, never really protesting his innocence or the ludicrous nature of the charges to the extent you would expect from an innocent man (though the commentary reveals that this was at least partly due to the instruction of his council), preening himself before a hand-held mirror in court, and soundly tripped up in the witness box by prosecution questioning. The film even ends on a speech from Damien that was doubtless instrumental in convincing a portion of the audience of his guilt. No doubt about it, these are three troubled kids, but not one piece of evidence emerges to connect them with the murder or suggest they have ever been involved in violence against others. Even the attempts to link them to some sort of satanic cult have no substance at all, the result of what is nicely described by the defence council as 'satanic panic'.

Berlinger and Sinofsky's largely impartial handling allows us to discover all this for ourselves and draw our own conclusions about the case, which has led to what the directors estimate as about twenty percent of the audience believing that the three are guilty. Either way, Paradise Lost: The Child Murders at Robin Hood Hills is a phenomenal documentary work, for the case, for its level of detail, for some very canny courtroom camerawork, and for being so sympathetic to both sides of the story, for its behind-the-scenes glimpse at the working of the legal profession. It also, more worryingly, shows that even in the 1990s it is possible for the justice system of the world's largest democracy to convict a person of a capital crime without a shred of plausible evidence connecting them to it. Even at 150 minutes it never for a second feels overlong, and though sometimes supremely uncomfortable and even upsetting, it is never less than compelling cinema.

Four years after the release of the first film, Berlinger and Sinofsky returned to West Memphis to make this follow-up documentary, and discovered that a great many things had changed in the intervening years. The families of the victims, with whom the filmmakers had previously had good relations, had been unhappy with the even-handed nature of the first film, and all refused to co-operate this time round. The notable exception is John Mark Byers, the stepfather of one of the murder victims and the first film's most colourful character, and the man that in the eyes of the accused and their families had himself become a focus of suspicion for the murders. Berlinger and Sinofsky were also denied access to the court proceedings, and almost none of the lawyers involved in the appeals process were willing to be filmed. On top of that, Berlinger and Sinofsky, now convinced of the innocence of all three boys, had decided to abandon their previously unbiased approach and throw their weight firmly behind the campaign to free them. Clearly, despite a strong similarity of tone, this was going to be a very different film.

It has to be said up front that while Revelations is unquestionably a strong work, it inevitably stands in its predecessor's shadow. It has little of the widespread and detailed access that made The Child Murders at Robin Hood Hills so remarkable, and the filmmakers' very focused viewpoint does tend to narrow their field of vision, although the non-co-operation of the victim's families is obviously a factor here. Where the film does get into potentially problematic territory is in its handling of John Mark Beyers, who here takes his performing for the camera to new heights and at times seems to be staging whole speeches and activities specifically to be viewed by Damien Echols. This does raise the question of whether he is faking the whole angry and distraught father act or simply reveling in the cinematic attention he is receiving, and just occasionally he comes across as a borderline nutball. Accusations fly from the convicted three and their families about Beyers' possible involvement in the killings, and the editing structure suggests at times that the filmmakers are also leaning into this viewpoint. This can't help but feel a little uncomfortable when you consider that it's not hard evidence that seems to put Beyers in the frame but his perceived abnormality, the very thing that convicted Damien Echols in the first place.

Nonetheless, the film prompts pause for thought on both sides, with much of the new information coming from criminal profiler Brent Turvey, who joins the defence team pro bono and quickly dismisses the idea that the genital mutilation of the victims was a skilled operation, something that contradicts a strategy used by original defence team to show that this could not have been done the accused. His seemingly crucial observation of a bite mark on one of the victims, which matches the dental impressions of none of the three convicted of the crime, also falls on deaf legal ears. It cannot be compared to Beyers' own bite because he has since lost every tooth in his mouth, the reasons he gives for which vary depending on who he is speaking to. Members of the West Memphis Three Support Group are presented in a gleamingly positive light, and indeed present their arguments with considerable confidence in their dealings with Beyers and the press. Damien, although visually transformed, remains surprisingly low key about the whole affair, though details of his early days in prison provide good reason for his apparent weariness.

Revelations is not as revelatory as the title suggests, and though a solid piece of work is essentially a postscript to the first film rather than a work of equal stature. Its detailed look at the work being done to overturn the convictions is in itself encouraging given the outrageous nature of the original trial, but time is now running out. With the appeal hearing chaired by the very same judge as the earlier trial, the three never really had a chance, and as Damien's last hope of avoiding execution draws near, Paradise Lost 3 – which will likely be the final chapter in the story, however it ends – is already in production. I, for one, am waiting with bated breath.

Framed in their original aspect ratios of 1.33:1 and shot largely on 16mm, with video footage for the courtroom scenes in the first film and the lie detector sequence in the second, this is a very respectable pair of transfers, with sharpness, colour and contrast all very pleasing, and grain, though evident, never intrusive or distracting. When you consider the state of some 35mm transfers, the job done here is admirable.

It should be noted that the transfer here are NTSC rather than the UK PAL standard. Though this is something owners of older, single standard TVs should be aware of, it does avoid any of those NTSC to PAL conversion issues, and is one of the reasons the transfer here looks so dapper.

Both films sport Dolby 2.0 stereo soundtracks that are clear and well mixed. The front speaker spread is quite good, but at its best when Metallica's music fills the soundtrack – impressively, they donated their tracks for free because they admired Brother's Keeper and believed in what Berlinger and Sinofsky were trying to do.

As if providing both films in the same package were not enough, Warp Films have graced this two disk set with a couple of extras, the first of which is a real beauty.

On disc one, an audio commentary is provided by directors Joe Berlinger and Bruce Sinofsky, and it's an absolute humdinger. Recorded specifically for this DVD on April 20th 2005, the pair talk without pause for the full 150 minutes of the first film and provide so much information about the production, the case, the trial, the participants, and the community that for a while they became a part of, that my notes on it went on for seven packed pages. There seems little point in reeling off all of the things that make this such an essential extra, save to say that the expansion of information provided by the two was like having a whole new 150 minute documentary on the case to mull over. Looking at my notes the thing that stands out instantly are the words, written in large capitals halfway through: "This is a great commentary!" Listen to the note book! If you've already seen the film and found the story it told even remotely interesting, the commentary alone, for my money at least, makes this release worth the purchase.

On disc 2 there is a Special Features section, but when you go into it you are presented with just one option, to 'Play Special Features', a misleading plurality given that there is just one such feature. Murder, Witches and Capital Punishment (21:46) consists of extracts from a presentation by Dennis Riordan to the Bar Association of New York on March 31st 2005. This is shot hand-held on 4:3 DV video with the sound recorded using the on-camera microphone, resulting in some issues caused by room acoustics and camera motor and handling noise. The framing is a bit iffy and the transfer displays plenty of compression artefacts, and the sound appears to be slightly out of sync with the picture. To be honest, the extracts reveal little that anyone who has seen the films and listened to the commentary will be surprised by, though the presentation of censored jurors' charts, and discussion of the influence of the supposedly inadmissible confession on their verdict is of interest. It also gives us our only look at Damien Echols' new wife.

If you have even a passing interest in the documentary format or in how justice can and is miscarried in modern day western society, then Paradise Lost: The Child Murders at Robin Hood Hills is essential viewing, and by association Paradise Lost 2: Revelations is an important and fascinating companion piece. By packaging the two films together – and at 150 minutes and 130 minutes respectively, these are substantial works – for the price of a single disc, Warp Films have done both films proud, with the inclusion of a superb commentary track for the first film proving the icing on the cake. Only available in the UK at present, with a wider European release planned for October/November, it's something of a surprise that this package is not available in the country in which it was made – at present, somewhat perversely, only the second film is available on DVD in the US. But then this could well be part of Warp Films' strategy in releasing an NTSC print on a disk with no regional coding, enabling it to be played without problem on Stateside machines. Wherever you're watching, this has to be one of the must-buy disks of the year. Full marks, Warp Films.