Families of two independent gold prospectors allegedly killed by security forces at a Tanzanian mine are taking their grievances directly to global markets, suing the London-based authority that certified metal from the deposit as ethically produced.

If successful, the legal maneuver in the case -- going after the London Bullion Market Association rather than the mining company, the gold refiner, Tanzanian authorities or the alleged killers -- could generate questions about whether gold produced amid violence or human-rights violations is seeping into the marketplace.

The case, involving Barrick Mining's North Mara mine, challenges the very system that companies, governments and consumers rely on to ensure the bullion and gold-based goods they buy meet accepted social-responsibility standards.

"It raises bigger questions of how much trust you can put into certifications," said Dorothée Baumann-Pauly, director of the Geneva Center for Business and Human Rights.

In court documents, the claimants allege the association, known as the LBMA, "negligently certified gold sourced from the mine as untainted by human-rights abuses," which "cloaked a pattern of violence at the mine and fueled ongoing violations."

The LBMA said it "denies the claim in full," and described the case as an attempt to make the association responsible for the actions of entities, such as the police, miners and refiners, it neither controls nor regulates.

The case is scheduled to go to trial Wednesday in London. The court has barred public release of the names of the dead miners or their family members.

The North Mara mine, which has both open-pit and underground operations, sits near Tanzania's border with Kenya, a short drive from the famous wildlife of the Maasai Mara and Serengeti National Park. Villagers living nearby have long sifted through the mine's waste rock hunting for overlooked gold.

The suit centers on two events in 2019. In July, a villager used a ladder to climb over a wall surrounding the mine's waste-rock area and "proceeded to search for gold-bearing rocks," according to the claimants' court filing. Mine security forces and Tanzanian police chased the prospectors away with "disproportionate and unjustified force, including the use of live ammunition and tear gas," the filing said.

The man escaped, but police were "lying in wait" and "violently assaulted" him, the filings said. He "suffered injuries consistent with a gunshot wound" to the leg and died from "a loss of blood," the filing said.

The first claimant in the lawsuit discovered his relative's body in the morgue, the court filing said.

Several months later, a second villager entered the mine grounds with some 200 other gold collectors, according to court filings. Police cleared them out with "disproportionate and unjustified force," including live ammunition, the filing said. The second man was shot in the back and died from his injuries, the filing said.

The claimants said in court documents that had the LBMA "complied with its common law duties, it would have stopped (or threatened to stop) issuing the relevant certifications, the abuses would have ceased and the claimants' relatives would probably still be alive."

Neither Tanzanian police nor the East African country's government, which has a 16% stake in North Mara, responded to requests for comment.

Toronto-based Barrick declined requests to comment on the specifics of the suit.

In a 2024 statement, the company cited an investigation by the state-run Tanzania Commission for Human Rights and Good Governance, which Barrick said found no human-rights violations related to security at the mine. That probe cited significant efforts by the mine to improve safety, including rules prohibiting private security officers from carrying weapons, Barrick said.

The company said earlier this year that it "maintains a zero-tolerance policy for human-rights violations by employees, contractors or any third parties acting on its behalf."

Barrick has posted a letter from its former chief executive, Mark Bristow, saying "we continue to address a number of legacy social and economic challenges in the area, including those related to resettlement, land acquisition and safety."

The LBMA, a nonprofit trade association, provides clean-gold certification to metal if it deems producers to have followed its Responsible Gold Guidance. It says it bases its decisions on information from gold refiners, verified by auditors, but doesn't carry out mine inspections itself.

The LBMA denied responsibility for the 2019 deaths. The LBMA said it sets standards for gold, but neither owns nor controls mines. The association said it has no authority over the Tanzanian police, and rejected the suggestion that it owed or breached any duty of care for North Mara miners.

"The case matters beyond gold," the LBMA said in a published statement. "Making industry programs liable for the conduct of organizations they don't control could weaken OECD-aligned responsible-sourcing programs across metals, minerals, garments and agriculture."

Leigh Day, the London-based law firm representing the families of the miners, said the LBMA certified as suitable-for-trading gold that came from the refinery that handled the mine's output in 2019, the year the deaths took place.

A spokesperson for the India-based refiner, MMTC-PAMP, a joint venture between the Indian government and a Geneva-based refiner, said the company "rigorously follows" LBMA guidelines and had been audited by a third party. The company no longer sources gold from the Tanzanian mine, the spokesperson said.

Leigh Day also represents 30 other claimants seeking recourse for alleged violence at the mine between 2022 and 2024. "Each year they have issued the refiner with a Responsible Gold Certificate despite a mass of evidence of alleged ongoing serious human-rights abuses at the North Mara mine, which supplied the refiner," Alex Wessely, a solicitor at Leigh Day, told The Wall Street Journal.