A movie about one of Australia's worst serial killings, the bodies in the barrels murders, screened for the first time last night at the Adelaide Film Festival.

So far the film has won praise from movie-goers, but some relatives of the 11 victims have vowed never to watch it.

A big crowd turned out to the premiere, including residents of Snowtown, the place where eight bodies were found in barrels 12 years ago.

Many people in the audience left the cinema dazed.

"Someone just described it as menacing. I'd have to agree with it; menacing, very eerie," one person said.

"I feel a bit weird and sad. But it's a great film and something that probably needs to be told. And if that's the truth well then we're better for it."

Another woman, with tears in her eyes, said it was very well done.

"It was very confronting and a bit scary because it's quite obvious that that sort of thing goes on and is probably still going on as we speak," she said.

Television actor Daniel Henshall plays John Bunting, the charismatic ringleader and one of the four men now in jail.

The story focuses on Bunting's influence over the youngest, Jamie Vlassakis.

"The film that we decided to make was purely based on the relationships that were formed, asking the question how and why this happened and how did a man like John Bunting come into a community and win them over and manipulate the situation into making them do what he wanted to do," he said.

Henshall said he was terrified at the killings and could not understand how something like that could happen.

Director Justin Kurzel says the film attempts to provide answers.

"There are many reasons I think why it happened. And hopefully the film offers up a debate and discussion about why that happened. I don't think there's one definitive answer," he said.

"But again I hope that the film just offers a different perspective for the audiences who see it."

He says he always tried to be respectful to the victims while making the film.

"Obviously Shaun and I right from the very beginning had at the forefront of our minds the sensitivity and the respect and the dignity that we always wanted to keep with the victims," he said.

South Australia victims' rights commissioner Michael O'Connell has been advocating for the relatives.

He says most of them do not want to see the film, but for his part he is satisfied with the final product.

"It's not a grotesque film. It has horror in it, but given that it could have been worse than what it is, I feel that there has been some sensitivity shown," he said.

For others like Paul Schramm, the senior policeman who led the murder investigation, the film was unnerving.

"I just feel sorry for the families that have to go through it again and indeed the investigators that had to put up with," he said.

"It shows you a glimpse of what investigators were exposed to in the long time that they were investigating."

Journalist Andrew McGarry covered the case for many years. He found the one graphic killing in the film hard to watch.

"That was difficult. I got through it but it wasn't something I'd like to repeat any time soon," he said.

His book on the Snowtown murders was used by the filmmakers.

"I'm pleased they took the approach they did. It was a harrowing drama but it wasn't a slasher pic," he said.

Snowtown is released nationally in May.