Grave robbing is the notorious practice of raiding burial grounds for items to sell on the black market.

It's not the label typically applied to archaeologists, who often encounter ransacked graves themselves during expeditions.

The Australian documentary Etched In Bone has exposed the great American-Australian Scientific Expedition of 1948 to the harsh light of the modern day.

"It's quite a simple story about an act of grave robbing," filmmaker Martin Thomas told ABC Radio Canberra.

"They got taken in the name of science, like so many human remains did.

"But these ones travelled a long way. They got taken to the Smithsonian Institution, which is in Washington DC."

Human remains were taken by one of the expedition leaders Frank Setzler, plundered from caves around Gunbalanya in west Arnhem Land.

Setzler featured in many images of the expedition and kept a detailed diary. ( Supplied: Smithsonian Institution )

He employed subterfuge against Indigenous people when taking the bones, according to his own diary entry on October 7, 1948.

"I paid no attention to these bones as long as the native was with me. During the lunch period, while the two native boys were asleep, I gathered two skeletons which had been placed in crevices outside the caves."

A particularly unsettling chapter of the expedition involved a cameraman filming Setzler during the ransack, to show back in the United States.

"It's even more macabre when you know that there were several takes," filmmaker Béatrice Bijon said.

"The one we've chosen for the film is just one of many.

"He's just acting — performing surprise that he's found these bones."

Martin Thomas, Joe Gumbula and Victor Gumurdul viewed archival footage in Washington DC. ( Supplied: Adis Hondo )

Taking the battle to Washington

In the 1990s, the US introduced laws that required the Smithsonian to release human remains to Native Americans, but exhibitions featuring Indigenous Canadians, Mexicans and Australians were exempt.

At the time, the Smithsonian had around 35,000 sets of human remains from all over the world.

The battle between the Smithsonian Institute and Aboriginal elders went on for nearly a decade, and was only sparked about 50 years after the original expedition.

The theft had almost passed out of living memory for traditional landowners, but photographs and footage from the time managed to stir the generations still living in Gunbalanya.

Lawman Jacob Nayinggul developed a strong relationship with the filmmakers. ( Supplied: Martin Thomas )

One of the most prominent figures featured throughout the documentary was senior elder and lawman Jacob Nayinggul.

"Jacob decided — it was really out of his impulse — that a film should be made," Thomas said.

"In the first place, it was more like a short film that gradually developed into a feature.

"We consulted the community all along. They've been amazingly supportive."

Filmmaker Béatrice Bijon says locals were open and friendly in sharing their stories. ( Supplied: Martin Thomas )

The filmmakers had to toe a delicate line between characterising the true nature of the 1948 expedition and respecting Indigenous people and their deceased ancestors.

One scene featured footage of Setzler clumsily trying to reconnect a jawbone to its skull before he absconded with the rest of the remains.

A central part of the dialogue was ensuring the community was behind some of the more graphic aspects of the documentary before it was released to the public.

Documenting and truth-telling

The strong relationship between Thomas and the elders meant he was invited to film both repatriation ceremonies at the Smithsonian and in Australia.

"It's so that people back in the home communities could see what went on in Washington," he said.

"There is a long history of historians writing Indigenous history entirely from the archives and never actually really talking to the people involved.

"It turned out they [talked] because of the advocacy, because of the really interesting ways that people even in the remote Aboriginal communities now are using media in their own lives."

The repatriation ceremony in 2010 featured cultural crossover between Indigenous Australians and Americans. ( Supplied: Martin Thomas )

Mr Nayinggul said during one of the ceremonies that the expeditioners had no right to take the remains.

"Stealing people's bones and taking them away for study ... well, it's no bloody good."

The sacred rituals of the Bininj people are prominently featured in the documentary, including the ceremony to talk spirits back to the land.

Native American Cheyenne elders were invited to the ceremony at the Smithsonian, with the deceased ancestors having rested in their land for decades.

The filmmakers endeavoured to include extensive footage of Nayinggul's ancestral country. ( Supplied: Martin Thomas )

Cultural taboos around showing deceased ancestors were also navigated by the filmmakers so the full story of the bone theft could be told.

"The people I've met are amazingly welcoming and integrative and want to share things," Bijon said.

"For the whole community ... it was absolutely essential that we showed that.

"To show how absolutely outrageous and shocking this was and how this should never have happened."

The National Museum of Australia set up its own repatriation program for Indigenous human remains.

Since the mid-1980s more than 1,100 Aboriginal and Torres Strait Islander people, and more than 350 cultural artefacts, have been returned to country.

There are still hundreds of skeletons held in other institutions around the world and the fight to reclaim them continues.

The documentary Etched In Bone premiered at the National Film and Sound Archive in Canberra.