HEFEI, China — China’s most widely anticipated trial in a generation ended Thursday less than eight hours after it began, with Gu Kailai — a daughter of the Communist Party’s “red aristocracy” and the wife of deposed charismatic leader Bo Xilai — confessing that she poisoned a British businessman who she believed threatened her son, according to an inside observer’s courtroom account.

The observer’s account, buttressed by an official court statement, detailed a dramatic case — including an e-mailed threat purportedly from the victim, Neil Heywood, and a description of how Gu poured a concoction of cyanide into Heywood’s mouth after he became drunk, vomited and asked for water. Finally, the observer said, Gu stood and addressed the court.

“I committed a crime that brought negative consequences to the party and the country,” Gu said, according to the courtroom spectator, a close associate of the defendants who spoke on the condition of anonymity because of the sensitivity of the case. Gu thanked her lawyers and the judge, as well as the prosecutors, who she said “opened the curtains a little bit, to reveal the hidden dirty secrets.”

Gu said calmly that she was ready to face her punishment, according to the courtroom observer, and asked for leniency for her loyal household aide, Zhang Xiaojun, who was also present. Prosecutors said that Zhang helped her carry out the murder but that Gu was the principal offender.

The case sparked China’s most serious political crisis in decades, derailing the expected promotion later this year of Bo. It also provoked anger among Bo’s many supporters and revealed long-
hidden fissures in the top ranks of the Communist Party’s normally secretive hierarchy.

With the swift trial of Gu — and a sentencing decision expected at a later date, following China’s ­usual practice — the party seems eager to move past the episode before a crucial leadership transition due later this year.

The trial was held in Anhui province, hundreds of miles from Chongqing, where the murder occurred. The only reporters allowed inside were from the state-run Xinhua News Agency and CCTV, typical for sensitive cases in this tightly controlled Communist country. Chinese media outlets relied solely on the Xinhua version of the trial, a terse dispatch based entirely on the official court statement, which provided few details about the proceedings.

In Chinese courts, unlike those in the United States, defendants often enter no plea. Instead, prosecutors outline their evidence and defendants are given a chance to speak — to rebut the charges, offer a competing narrative or suggest mitigating factors. In Gu’s case, the bland court statement said she “did not contest” the prosecution’s case. However, the courtroom observer went further, saying in an interview that Gu confessed.

The court statement said that Gu — who according to close family associates has suffered from severe depression in recent years — was not mentally stable at the time of the murder and that “her self-control was weaker than a normal person’s.”