When she was growing up in Australia, Kitty Green became obsessed with the 1996 murder of six-year-old pageant queen JonBenét Ramsey in Boulder, Colorado.

“I was 12 or 13 watching it on television and the pageantry and the whole thing was so amazing to me,” the rising young director of Netflix film Casting JonBenét recalls. “I’d never seen anything like it. I thought that was what every American family was like, so I had this very bizarre idea of America. After that every time I met someone from Colorado I’d ask, ‘Who killed JonBenét Ramsey?’ And they would always have a different reaction. I met a guy from Boulder on a ski lift in Japan and he was like, ‘My God I don’t want to be chatting about that.’ But he had this crazy drug ring theory and he then went on for 10 minutes explaining it to me. I was like, ‘Wow, there’s something there’.”

As the daughter of Patsy and John Bennet Ramsey, the blonde angelic-looking JonBenét (her name is a portmanteau of her father’s first and middle names) came from a wealthy family. In the middle of Christmas night 1996 she was strangled and hit on the head, though her body was only discovered in the family’s basement eight hours after she was reported missing.

Initially the police were investigating her kidnapping, as there was a ransom note asking for $118,000. The note was soon considered to be dodgy and possibly part of a cover-up by her mother (1977’s Miss West Virginia, who had entered her daughter in beauty pageants). Ultimately this theory was dismissed from the investigation.

Later, an American arrested in Thailand in 2006 reportedly confessed to the murder, but this was also discounted.

Green’s work is described by Netflix as “a hybrid of fiction and non-fiction filmmaking”. It takes a look at the unsolved case via interviews with mostly non-actors in Boulder as they audition for parts in a film about the murder.

“What we are looking at rather than the murder is the community surrounding the case, the legacy, the mythology,” Green explains of her unconventional approach. “JonBenet has become such a cultural icon. I went to the grocery store and she’s still on the cover of the tabloid magazines 20 years later. So I was just trying to tap into this cultural obsession. We found it always came from personal places — people can’t really let the story go because they connect to it in so many different ways.”

Green conducted 200 interviews for the film. “Everyone would kind of say the same thing, but some you would remember. ‘Oh that was the BDSM sex guy’. You don’t forget that.”

A fan of the films of Errol Morris, the diminutive Green sat behind her tiny camera in the hope of not intimidating her subjects.

“We created this intimate space because people were confessing things and it’s quite a vulnerable position to be in,” she notes. “We made sure it was a quiet room and basically I was the only one in the room with them and we had a sound team and a production designer behind a wall, so they felt safe and comfortable.”

The important thing was to be very prepared, she says.

“I picked the key moments in the Ramsey case, the most interesting subjects and suspects and then we drip fed the information. So you get the ransom note, you get the 911 call, you get the autopsy report — without having to actually show a single frame of the actual family or a single frame of the actual little girl, which was the aim. We wanted to leave the family alone, we wanted to make something that’s unique and different so you can get the facts and know who is involved. All of that was very structured and figured out in the beginning.”

Green used a team of her comptatriots to make the film.

“Between 60% and 70% of the film was shot by a team of five Australians so the film has a unique outsider perspective on the story and on American culture. People come up to me and say that they don’t think an American couldn’t have made this film and certainly we wanted to pick things apart and examine them.”

At the film’s premiere at the Sundance festival, the participants were delighted to see themselves on the big screen. “We ended up with a cast of 72 and around 35 of them came to the premiere. They all sat with us and it was incredible to see them watch it for the first time. They were overwhelmed in tears and had a great time watching it and posted it on their Facebook pages.”

The image of the gaggle of girls lined up to play JonBenét and wearing one of her pageant dresses is priceless. “We were really honest with the parents about it and I’d made a lot of films with children and a lot of feminist films,” she explains, referring to films including Ukraine is Not a Brothel and The Face of Ukraine. (Green is of Ukranian heritage.)

“When we explained the approach and that we were making something we’d like to call a work of art, the parents came on board. They had to trust us and we had to be very honest for that relationship to work.”

Netflix picked up Casting JonBenét before Sundance and Green was ecstatic.

“Netflix is great because it’s global and everyone has it in their living rooms,” she says. “People often won’t buy a documentary from iTunes but will watch it on Netflix because it’s just there.”

So who killed JonBenét Ramsey? “That’s not what the film’s about,” Green replies. “We always answer that with, ‘We’re never going to know’. Hearing so many stories has made me more confused than when I began. Everybody has a different theory on it. There is absolutely no way this case is going to be closed. In the final scene with all the actors on set we’re trying to close the book on it, saying ‘This is enough, let’s let this little girl rest now’. It’s been too much and it’s everywhere and there’s no point speculating. That would be my opinion on it.”

Certainly, tragedy has surrounded the family. After the murder the Ramseys moved back to Atlanta, Georgia where JonBenét was born. Patsy died at the age of 49 from ovarian cancer in 2006 and was buried next to her daughter.