Director Amy Berg on her film Every Secret Thing

Some of the 'wives' of Warren Jeffs, jailed leader of the Fundamentalist Church of Jesus Christ Latter Day Saints (FLDS). Picture: Contributed

Yeah, I guess I am pretty busy,” says Amy Berg. On the phone from Los Angeles ahead of her arrival at the Edinburgh International Film Festival, the documentary filmmaker behind the Oscar-nominated Deliver Us From Evil and the Peter Jackson-produced West of Memphis may be understating things just a little.

After all, she’s talking to me on the day An Open Secret, one of four new films she’s releasing this year, is hitting US cinemas amid a storm of controversy for its unflinching exposé of child predators operating within Hollywood.

She’s also in the final stages of completing her seven-years-in-the-making documentary about Janis Joplin. “I’m trying to finish that before I fly to Edinburgh,” she says. “I love Janis Joplin. It’s so nice to be in the editing bay with her and her music every day.”

When she arrives in Edinburgh, she’ll join the likes of Karen Gillan, Natascha McElhone and Jessica Hynes on the jury for this year’s Michael Powell Award. And this is on top of premiering her other two new films: the harrowing documentary Prophet’s Prey, about a fundamentalist sect of the Mormon church, and her fiction debut, a crime drama called Every Secret Thing, starring Elizabeth Banks, Diane Lane and Dakota Fanning.

“So I guess I’m going to be pretty busy there too,” she laughs.

Berg certainly seems to thrive on this kind of cinematic plate spinning. Having cut her teeth as a broadcast journalist for CNN (among others), she’s emerged in the last few years as one of America’s foremost documentary makers: doggedly exposing systemic abuse and corruption.

Prophet’s Prey, for instance, which counts Ron Howard as one of its executive producers, is very much a continuation of themes first explored in Deliver Us From Evil, her investigation into child abuse within the Catholic Church. This time, she zeroes in on Warren Jeffs, the currently incarcerated leader of the Fundamentalist Church of Jesus Christ of Latter-day Saints (FLDS), a fringe Mormon group that re-introduced polygamy and, under Jeffs (who took upwards of 90 wives, some as young as 12) used the twisted rationale of religious dogma to molest children. It’s a sickeningly compelling story, not least because Jeffs continues to exert an influence over his “congregation”.

“That’s why I was interested in shedding some light on it, because when I heard the pitch, I almost couldn’t believe there was this man in prison who was still able to lead 10,000 people from his prison cell.”

Jeffs’ criminal notoriety is rammed home in the film when he’s placed on the FBI’s most wanted list next to Osama Bin Laden. With the FLDS also buying up huge swathes of land across the US and constructing heavily guarded compounds to shield their activities from prying eyes, the parallel to Islamic extremism is clear to see.

“Thank you for saying that,” says Berg. “This isn’t really a film about the LDS church and its problems. It’s a film about extremism. Any extremist organisation has the same kind of tentacles, and we see the same themes emerging in these types of stories so you have to point them out.”

The brainwashing that goes on is a case in point. As detailed in the film, women within the FLDS community are completely subjugated, families are cut off from the outside world and children are indoctrinated from birth. “They know literally nothing else except what they’ve been told. And now that many of them are starting to escape the group, they’re having to reintegrate themselves into society. That concept was something that was interesting to me, so I just started looking into it and found the voices that had not been heard before were worth hearing and their stories worth telling.”

This notion of people having to re-acclimate into society is explored in Every Secret Thing as well – although here we’re seeing it from more of a criminal point of view than a victim’s. Adapted from Laura Lippman’s best-selling thriller, the Frances McDormand-produced drama stars Diane Lane as Helen, a school teacher whose 18-year-old daughter, Alice (Danielle Macdonald), has just been released from juvenile detention following her participation a decade earlier in the death of an infant at the hands of fellow childhood outcast Ronnie (played as a grown-up by Dakota Fanning). “It did feel like a natural progression,” Berg says of the move into drama, particularly because she made the film after completing West of Memphis, her investigation into the notoriously shaky conviction of three teenagers for the murder of three little boys in Arkansas in 1993.

British viewers, however, are more likely to be reminded of the case of James Bulger, the Merseyside toddler abducted and murdered by two ten-year-old boys the same year. “I studied that case intensely when I read the script,” says Berg. “I think the scariest part of that for me was that there was no information about the convicted murderers because they were juveniles. I think it’s interesting that two 18-year-olds can be put back into society with that type of a record and nobody in the public can know about it.”

In the film, the girls’ release coincides with the disappearance of another child, a plot development that opens the door to a meditative procedural as the lead detective, played by Elizabeth Banks, is forced to confront her own history with the first case. Berg describes the ensuing film as more of a psychological study of women than a “ticking-clock, missing-baby thriller.”

“It’s not Prisoners,” she says, referencing the big budget Hugh Jackman thriller to which Every Secret Thing has been lazily compared. “This a $3 million budget character study and that’s how we approached it.”

That arthouse approach certainly gave her the freedom to build the film around a quartet of flawed, complex women who aren’t necessarily redeemed by the movie’s end. “I think that’s a step in the right direction of honest depictions of women in film and that’s one of the reasons I liked the script.”

Berg’s currently in the process of developing another dramatic feature, this time about the 1978 Jonestown massacre told from the point of view of a female survivor. Before that there’s the aforementioned An Open Secret, which she reportedly had a tough time getting released thanks to its controversial subject matter. As she points out, though, it’s not about creating controversy; it’s about finding solutions. “You’ve gone through this in your country with the whole Jimmy Savile thing. That was such a big thing, so far after the fact, and I feel this story identifies a lot of problems that are going on right now in Hollywood.”

She reckons this campaigning aspect to her filmmaking comes from a deep-rooted hatred of bullying as much as it does her background in journalism. “I really feel like that’s where I can be an asset.

“But it’s not the only thing I’m interested in,” she adds, pointing to the Joplin documentary – though even her story, she concedes, has an element of sticking up for the underdog in it. “She was ridiculed for speaking up and trying to fight for people who didn’t have a voice and that really dictated her future. I guess I just want to continue to do films that matter and are entertaining. That’s what’s important to me.”

• Every Secret Thing screens at the Edinburgh International Film Festival on 19 and 20 June; Prophet’s Prey screens on 20 and 21 June. For tickets and times visit www.edfilmfest.org.uk