Ralph Blumenthal and Tom Mashberg, The New York Times

They have long been oddly far-flung collaborators. She was a Colorado museum consultant known for her esoteric lectures on ancient gold adornments or nomadic Chinese tribes. He was a buccaneering Bangkok art collector who trekked through Cambodia’s war-ravaged jungles in the 1970s, exploring moss-encrusted temples built a thousand years earlier, during the heyday of Khmer civilisation.

Over the course of a 30-year friendship, Emma C Bunker, 87, and Douglas AJ Latchford, 86, became authorities on Southeast Asian antiquities whose approval could ensure an object’s value and legitimacy. Together they wrote three seminal volumes – Adoration and Glory: The Golden Age of Khmer Art, Khmer Gold and Khmer Bronzes – that are core reference works for other experts.

The books contain letters of tribute from Cambodian officials who applaud the pair’s dedicated research and support for the National Museum in Phnom Penh. In particular, they hail Latchford, who has donated rare artefacts and money to the museum, acts of generosity that led the government to knight him in 2008.

But in a criminal complaint filed by the Manhattan district attorney in December in New York, Latchford and Bunker are identified less respectfully – as Co-Conspirator Number 1 and Co-Conspirator Number 2.

The complaint says that over a period of years the co-conspirators and others helped a prominent New York gallery owner, Nancy Wiener, falsify the documentary history of looted Cambodian relics, making them easier to market.

“Misrepresenting the true provenance of an antiquity is essential for selling stolen items in the market,” Brenton Easter, a federal agent, said in the complaint.

Neither expert has been charged, and neither is identified by name in the complaint. Latchford is described in the complaint as “an antiquities dealer based in London and Bangkok” and Bunker as “a research consultant for an American museum”. But people familiar with the case have confirmed their identities.

The accusations in the case are hardly novel in the annals of art fraud. But experts say this case highlights the vulnerabilities of the art world, where authenticity and ownership disputes are common and where scholarship often provide the imprimatur that dealers need to close sales.

“The market couldn’t function without these people,” said Neil Brodie, a researcher who studies the theft and trafficking of cultural objects. “When you have an opinion from someone like Emma Bunker and you’re a purchaser or a collector, you’re pretty sure it’s genuine.”

Wiener, 61, who has pleaded not guilty, is accused of using her business “to buy, smuggle, launder and sell millions of dollars worth of antiquities stolen from Afghanistan, Cambodia, China, India, Pakistan and Thailand”.

The complaint asserts that the two experts benefited by aiding Wiener. It cites an email seized by investigators in which Latchford tells her he gives bronze statues to Bunker in exchange for false provenances. As for Latchford, the complaint says some of the phoney provenances were used to help market items he sold to Wiener or had bought in tandem with her.

Bunker said in a phone interview from Wyoming that she did not recall the matters cited in the Wiener case. “I never gave a cover for anything,” she said, and referred questions to a lawyer who did not return calls.

Crumbled in the jungle?

Latchford, a Mumbai, India-born British citizen, did not respond to requests for an interview. In previous interviews, Latchford has denied wrongdoing and defended his collecting practices as the norm for an era when far less rigour was attached to provenance and documents.

He said in 2012 that Westerners who acquired Southeast Asian objects during the decades of war in Cambodia and Vietnam should be seen as rescuers who lavished care and scholarship on objects that might have crumbled in the jungle.

“If the French and other Western collectors had not preserved this art, what would be the understanding of Khmer culture today?” he said.

The three books Latchford has written with Bunker display hundreds of Khmer items deities, mythic creatures and royal treasures in sandstone, gold and bronze that are as unique and valuable as any found in Cambodia’s National Museum.

Cambodian officials say they have no record of most of the objects and rely on the books for confirmation of their existence. Asked about this in a 2014 interview, Latchford said they were held by private owners who trusted him to keep their identities confidential.

The case now entangling Bunker and Latchford is just the latest to roil the world of antiquities. Long a partner with her mother, Doris, who died in 2011, Wiener is charged with criminal possession of stolen property and conspiracy, the result of a raid on her gallery last year that investigators say netted thousands of emails and other documents. One item that Latchford had consigned to Wiener for sale was seized at the time.

The complaint says she used “a laundering process that included restoration services to hide damage from illegal excavations, straw purchases at auction houses to create sham ownership histories, and the creation of false provenance to predate international laws of patrimony prohibiting the exportation of looted antiquities”.

The complaint says that some of the seized emails show Latchford and Bunker concocting phoney ownership histories. In one, from November 2011, Bunker asked Latchford what sort of document Wiener needed regarding a bronze 10th-century Khmer statue of a Naga Buddha that Latchford was selling the dealer for $500,000. The Wiener gallery was preparing to resell it for $1.5 million.

“I wonder,” Bunker wrote to Latchford, “whether it might not be better to say that you bought it from a Thai collector when you first moved to Bangkok in the 1950s. Who, other than Neil and Yothin, knows when you acquired it.”

A month later, Bunker sent Latchford a provenance letter in which she wrote “I first saw the Naga Buddha in Douglas Latchford’s London flat sometime in the early 1970s, when I was there on my way to China.”

She identified herself in the letter as “Research Consultant Asian Department Denver Art Museum”.

In another instance, according to the complaint, Wiener and Latchford jointly bought an 11th-century statue of the Hindu god Shiva in 2008 for $250,000 from a supplier.

But when they consigned it to Sotheby’s for sale in 2011, Wiener told the auction house it had been purchased in 1968 from another antiquities dealer, Spink & Son. The complaint said that they invented the ownership history and that some markings on the statue, indicative of damage and repair, led investigators to conclude the statue was looted.

The piece sold at auction in 2011 for $578,000.

(Sotheby’s said that it had not known of any phoney provenance and that such markings on ancient items are common and not necessarily evidence of looting.)

‘The Collector’

Five years ago, Latchford and Bunker were cited in a civil case involving a 10th-century Cambodian statue. Sotheby’s was hoping to sell the statue in New York on behalf of a Belgian collector for an estimated to $2 million to $3 million when US officials moved to seize it, asserting it had been looted from a temple in the 1970s during the Khmer Rouge genocide.

Latchford and Bunker were not named in the court papers, but the government identified Latchford as “The Collector”, an earlier owner of the piece who had first purchased it in the 1970s after the statue had been hacked from its temple site, its feet left behind. Bunker was cited as “The Scholar” who had counselled Sotheby’s about the sale.

In emails from 2010, before the piece was put up for sale, messages show Bunker telling Sotheby’s her concerns about the sale.

“The Cambodians in Phnom Penh now have clear evidence that it was definitely stolen from Prasat Chen at Koh Ker as the feet are still in situ,” she emailed a Sotheby’s officer. She counselled against selling it at public auction because “the Cambodians might block the sale and ask for the piece back”.

A few weeks later, just back from Cambodia, Bunker reported that the Cambodians had no plans to ask for it back. Sotheby’s could proceed with the sale, she advised, “but perhaps not good to show or mention the feet still in situ at Koh Ker in the catalog”.

Sotheby’s ended up putting the statue on the cover of its sales catalogue. But the Cambodians did object, and the US attorney in Manhattan at the time, Preet Bharara, initiated a seizure action in court. The auction house challenged whether the piece had been looted, but the case was settled and the statue was ceremonially returned to Cambodia in 2014.

At the time of the dispute, one expert spoke to how the passage of time had created new legal parameters that veteran collectors and dealers would need to observe.

“We live in a different world,” said Matthew F Bogdanos, a Marine Corps Reserve colonel who had led the hunt for ransacked treasures during the Iraq War, “and what was acceptable 50 years ago is no longer so”.

As it turns out, Bogdanos, who is also a prosecutor in the office of Manhattan District Attorney Cyrus R Vance Jr, is leading the Wiener investigation.