Meet the mass murderers | Joshua Oppenheimer

As luck would have it - and as part of the ongoing International Film Festival - St James Cavalier is currently screening The Act of Killing - arguably the most shocking and important documentary of the noughties.

Showing at the Cavalier for one last time next Thursday, Joshua Oppenheimer's film has an instantly attention-grabbing premise: allow the perpetrators of some of the most brutal war crimes of the past century to tell their story - not just verbally, but through cinematic scenes that they would script, direct and star in, aided by Oppenheimer and his crew.

Focusing primarily on three figures responsible for the murder of thousands of alleged 'communists' after the Indonesian government was overthrown by a military dictatorship in 1965, The Act of Killing has recently been listed among the 15 documentaries in the running for the 2014 edition of the Oscars.

I'm surprised that Oppenheimer does in fact appear to be taken aback by the news that The Act of Killing has been shortlisted for the Oscar. Even that very same piece of news often came accompanied with a still from Oppenheimer's film: hinting that it certainly appears to be in the lead among its documentary peers...

"The thing is, when you set out to create a work that's so unsettling and dark, you have to have a pretty bleak view of humanity to begin with," he tells me over Skype.

"But on the other hand, you could never sustain the energy for such a work unless you're also hopeful. My hope is that by looking at some of the most painful aspects of ourselves, we would somehow then be able to confront our biggest problems. So there's a kind of optimism that underpins the whole effort..."

The film is certainly a potent psychological cocktail, as well as being a searing expose of a brutal military regime. Zooming in on a group of top-brass executioners (read: gangsters drafted in as enforcers by the government), it confronts viewers with a deeply uncomfortable fact: that human beings are capable of justifying even the most brutal atrocities to themselves, provided that they are in turn justified by some overarching political or ideological narrative.

"The film bears witness to how maintaining of the lies we tell ourselves leads to a moral vacuum - a downward spiral of evil and corruption," Oppenheimer says.

"You now have to blame your victims - because that's the excuse, 'they deserved it' - and that allows you to oppress them, and you have to kill again. Because if the army tells you, 'Ok - for the same reason you killed the first group, now kill this second group'... if you refuse the second time it's equivalent to admitting it was wrong the first time.

"And the reason you need to maintain the lie is not because you're a sadistic monster, but because you're human... and being human, you're moral, and you know what's right and wrong, and you don't want to live with the tormenting effects of guilt."

Among the killers interviewed by Oppenheimer, one looms largest above all: Anwar Congo, a highly respected death squad member now tormented by nightmares and a sense of encroaching doom over what he did. It's to the film's credit that Anwar's journey is never resolved in a neat, easy way, though Oppenheimer admits being "disappointed" by his subject's apparent inability to achieve complete self-awareness.

"There were certain moments where it became clear that he was starting to finally empathise with his victims," Oppenheimer says, mentioning a particular scene in which the killers were re-enacting the slaughter of an entire village,

"but then his reaction to that would be to revert to his darkest self..."

READ MORE: Film Review | The Act of Killing

The Act of Killing is an unflinching film, and Oppenheimer doesn't shy away from showing us Anwar at his worst. The scene in question depicts Anwar butchering a teddy bear - representing a suspected communist's young child - and is signaled as a kind of 'point of no return' for Anwar. It was also, as it turns out, a traumatic moment for Oppenheimer himself.

"As we we're shooting that scene, I was standing about a metre away from the set, and I began to notice, to my horror, that I had begun to cry. Then at some point we had to stop - to adjust a microphone or a light or something - and Anwar noticed that I was crying and he asked, "Josh, are you okay?" and I said, "yes," though I wasn't really..."

It's hardly surprising that such a project would take a psychological toll on Oppenheimer, and he describes how, following the shooting of that pivotal scene, he began to suffer from nightmares that lasted a good eight weeks.

This is of course only a fraction the damage someone like Anwar would have suffered, and the toll is definitely evident on him too. The teddy-bear-dismembering scene is also filmed in reverse: with Anwar having the chance to occupy the role of the victim as well as the perpetrator... and being visibly and deeply affected by the experience (if never quite making peace with his past sins).

Perhaps what sticks in the mind of most viewers after they've watched The Act of Killing - haunting them like particularly grisly detail from a horror film - is the fact that they're made to identify with the killers as human beings, who are living their lives as normally as they can despite their entirely reprehensible actions.

Oppenheimer recounts an episode from the production's early stages - back in 2003 - to explain how he himself first began to inhabit this unsettling, but truthful, mental space.

Having done some filming on an Indonesian plantation, Oppenheimer then visited one of the militia's killers in their home. The perpetrator proceeded to demonstrate how he would murder people during the 'communist cull' in the 60s, in his living room, and in full view of his wife and daughter.

"I left their house in complete shock, mostly because of the smiling, boastful way in which the man spoke about what he'd done. But then, around half an hour later, his wife showed up at the place I was staying with a plate of fried bananas as a gift. I accepted it very politely, and then got rid of her as quick as I could - and I threw the bananas away, because I felt that everything that family touched was tainted.

"But then, the following day, I saw their granddaughter playing outside my house, and I began to think about what I did, and I began to regret having thrown the bananas away.

"I realised how easy it was for me to treat the whole family as radically 'Other', and I decided I would never do that again, that I would try to empathise, to understand.

"Because I realised that the main reason I did that was to reassure myself that I was not like them. And while I hope that I would never make the same decision as Anwar made if I grew up in Indonesia in the 50s, I know that I'm extremely lucky to never have to find out."