BEIJING — Gu Kailai, the wife of disgraced Chinese politician Bo Xilai, has been formally charged with killing a British businessman, state media reported Thursday, in another twist of the biggest scandal to hit China’s elite in recent years.

Gu and a person previously described as a household employee, Zhang Xiaojun, are accused of poisoning Neil Heywood last November after conflicts “over economic interests” and worries about Heywood’s “threat to her son’s personal security,” according to the state news wire Xinhua.

While the indictment itself isn’t a surprise – official media said in April that the two were suspected of killing Heywood and had been “transferred to judicial authorities” – it signals a step forward in a turn of events that have shocked the country’s highest levels of power.

The Xinhua item stressed that authorities feel confident about their case against Gu, which could bring the death penalty. The Chinese Communist Party almost certainly has predetermined the outcome. Chinese trials aren’t open to the public, though family members may be allowed to attend.

“The facts of the two defendants’ crime are clear, and the evidence is irrefutable and substantial,” Xinhua reported, saying the pair was charged “recently.”

While Xinhua said a trial date in China’s eastern Anhui province hadn’t been set, a Reuters report quoted a family lawyer as saying it probably would start on Aug. 7 or 8.

It remains far from clear what will happen to Bo Xilai, who wasn’t named in the Xinhua release.

Gu is the daughter of a prominent revolutionary general, and her husband the son of a prominent party elder. Until recently, Bo was widely seen as a leading candidate for a slot on the nation’s ruling Politburo Standing Committee, which is expected to see seven of its nine seats turn over this year. But he was stripped of his position as the party chief in the sprawling southwestern city of Chongqing and booted from the 25-person politburo in the months after his former police chief fled to an American consulate in February.

Sources in Chongqing later claimed that the recently demoted police chief, Wang Lijun, had decided to bolt from the city after a confrontation with Bo sparked by his airing of suspicions that Gu had killed Heywood. After emerging from the U.S. consulate in Chengdu, a city to the northwest of Chongqing, Wang is thought to have cooperated extensively with Chinese government investigators.

Bo so far hasn’t been charged with any crime. In announcing his removal from the politburo in April, Xinhua said only that he stood “suspected of being involved in serious discipline violations.” How and when to resolve his fate is a particularly sensitive issue given the upcoming Communist Party congress, which is scheduled for sometime before the end of the year and will usher in the once-in-a-decade transition of top leadership.

Heywood reportedly functioned as a middleman for the family, arranging business deals and allegedly working to get their son into the Harrow School, an elite British boarding school. There’s been rampant speculation that Heywood helped Gu, a well-known lawyer, transfer large amounts of money out of China.

Heywood’s death in a Chongqing hotel room initially was reported as due to natural causes, related either to overconsumption of alcohol or heart complications, and his body was cremated.

Another reputed former member of Gu’s inner circle, French architect Patrick Henri Devillers, flew to China last week from Cambodia to serve as a witness in the investigation. Beijing had requested that Devillers be extradited, resulting in his detention by police in Phnom Penh, but he said in a taped statement released by Cambodian authorities that he was traveling to China by choice.

During his reign as the party secretary of Chongqing, Bo cultivated a populist appeal and, relative to the typically buttoned-down world of Chinese politics, brash ambition. That included a harsh police crackdown on people accused of being criminals – which critics charge was a way of getting rid of his enemies – and a push for a revival of Mao Zedong-era culture.

It was an approach that alarmed some in Beijing, though it also made him popular with many average people in Chongqing and elsewhere.