Fallen Chinese politician Bo Xilai's spirited self-defence in court was likely condoned by the authorities to give a varnish of fairness to a trial in which the verdict is already decided, analysts say.

Bo, who was tipped for top office ahead of a once-in-a-decade leadership transition last year, hurled insults at his accusers and calmly tried to bore holes in the prosecutors' logic.

His display on the first day of his trial Thursday at the court in Jinan was in contrast to the meekness usually shown by defendants in high-profile Chinese cases.

But analysts said that while Bo's being allowed to speak out gave the process a sheen of transparency, it will have no effect on the result.

Steve Tsang, an expert on Chinese politics at Britain's University of Nottingham, said the trial had been agreed on by the top leadership with the verdict and sentence already determined.

"Therefore, almost whatever he does the court is going to act in accordance with the script prepared beforehand," he said.

Bo was allowed to speak out via the release of near-real-time court transcripts sent via social media -- although it was not clear how complete the accounts were.

"I think the authorities will say that they have tried to give him an opportunity to defend himself," said Willy Lam, an expert on Chinese politics at the Chinese University of Hong Kong.

"So it gives some credence to the spin which Beijing is trying to give this, that they are now more willing to observe the rule of law and so forth."

On Friday the state-run China Daily's front-page headline read: "Bo Xilai denies charges of bribery." A second story was titled: "Case breaks ground for transparency."

The hearings also give Bo, a scion of Communist Party royalty as the son of a legendary party figure, a chance to save some face with his supporters.

"You can say that Bo has maintained his reputation as a maverick, as a charismatic leader who challenges party authority sometimes," Lam said.

"So I think you can say that he has won something, at least, particularly compared to his wife and other victims of power struggles."

Bo's spouse, Gu Kailai, was convicted last year of the murder of British businessman Neil Heywood, whose death sparked the drama that led to her husband's downfall.

"He does strike a pose of defiance. But I don't think either way it will affect the outcome," Lam said.

He Weifang, a law professor at the prestigious Peking University, said the court must have received permission from higher authorities to publish so much of the dialogue.

"I think that officials think that by doing it this way they can be more persuasive, and can tell people more clearly that the process is just," he said.

"Of course it's not a completely fair process," he added, while expressing surprise at what he called "the comparative level of openness".

Nottingham's Tsang said Bo was clearly aware of what was going on.

"He knows the system, he knows how it works and therefore he will know that he is probably going to have a jail sentence not less than what his wife got, so at least 15 years," Tsang said.

"He will not be executed and he will not regain his freedom while the current political set-up remains as it is."

Authorities were taking a "calculated risk" by allowing Bo to speak out and potentially drum up support for his cause, Tsang said, but he emphasised they have most probably reached a deal with him already and that he has "in principle" agreed.

Observers have speculated that Bo wants to protect his son, Bo Guagua.

The son is studying law in New York -- and was himself implicated in alleged bribery during Friday's proceedings.

Bo knows that he can rely on a long-standing practice in the Communist Party that, since the Cultural Revolution, the next generation is left exempt from internal factional and power struggles, Tsang said.

"If the top leadership now goes back to punish Bo Guagua for his father's defiance in court, then they are actually changing the game somewhat," he said.

"And then they will have to start to worry about if they themselves fall from power will their relatives, will their next generations, also suffer?

"That is a pretty strong deterrent to the top leadership from punishing Mr Bo by doing something about his son and that may well in fact be the calculation behind Mr Bo's defiance.

"He's got nothing to lose."

Bo tells China corruption trial his wife is 'insane'
Jinan, China (AFP) Aug 23, 2013 - Fallen Chinese politician Bo Xilai described his wife as "insane" Friday after his corruption trial heard video testimony from her implicating him in bribery, in a case that is gripping the communist-run country.

Gu Kailai, once a high-flying lawyer but convicted last year of murdering Neil Heywood, the British businessman whose death sparked the corruption scandal that brought Bo down, looked nervous in the pre-recorded video.

She described telling her husband of a series of bribes, but Bo told the court she was mentally unstable and had compared herself to a historical Chinese assassin, telling him she felt "heroic" when killing Heywood.

The scandal erupted in advance of a generational shift of power atop China's Communist Party and Bo's feisty performance over the two days of his trial has astonished a public unfamiliar with the open airing of top-level intrigue.

In her testimony Gu said she feared Heywood would kidnap and kill the couple's son Bo Guagua in the United States.

She looked thin and pale during the questioning, recorded earlier this month. It was played in court the day after Bo pleaded ignorance to her dealings, and released by the court on Chinese social media, where it had more than one million views in an hour.

Asked if Bo knew about airline tickets and other items provided by business tycoon Xu Ming -- who prosecutors said had bribed him to the tune of 20.7 million yuan ($3.4 million) -- Gu at first said "he should have been aware".

Pressed by the questioner, she said: "I told him."

According to transcripts of Friday's hearing released by the court in Jinan in eastern China on Sina Weibo, a Chinese equivalent of Twitter, Bo told the court: "She is insane now and she often tells lies.

"The investigators placed enormous pressure on her to expose me when she was mentally disordered."

She had compared herself to Jing Ke, who more than 2,000 years ago tried and failed to kill the man who would become the first emperor of a unified China, he added.

The claim was "sufficient to prove that she was mentally disordered", Bo said.

State-run media have proclaimed the proceedings a mark of transparency.

Bo, once one of China's highest-flying politicians, faces charges of bribery, embezzlement and abuse of power which emerged after the lurid scandal triggered by Heywood's death.

Bo presented an unexpectedly spirited defence against bribery charges as the trial began on Thursday, comparing one witness, businessman Tang Xiaolin, to a "mad dog" who appeared to have "sold his soul".

State broadcaster CCTV on Friday released video of one of the trial's most dramatic moments, when Bo cross-examined Xu Ming.

In a colourful exchange -- which touched on a football club, a hot air balloon and the purchase of a French villa -- Bo argued that the tycoon had not made him aware of the transactions.

Bo's populist politics won supporters across China but alienated top party leaders who saw his brash approach as a return to a bygone era of strongman rule.

Backroom political discussions ahead of the trial have ensured that a guilty verdict from the court is almost certain, with a lengthy prison sentence likely to follow, analysts say.

At least five relatives attended the hearing, including Li Wangzhi, Bo's son from his first marriage. Li released a statement to The New York Times praising his father's courage in speaking out, while thanking the authorities for allowing him to do so.

"I thank the party central authorities and the court for giving the defendant greater rights to a defence and freedom than he had expected, allowing my father to speak his true mind," he said, adding he was "proud" of his father.

"I hope that my father will continue to respect the law, and that the law may also respect the facts, and leave the people an explanation, leave history an explanation, and leave his son an explanation too," said Li, who is in his mid-30s and has reportedly not seen his father for several years.

Bo Xilai's own father, revolutionary military leader Bo Yibo, also gained a reputation for defying the authorities, refusing to admit any wrongdoing while he was jailed and abused during the Cultural Revolution.

Police -- uniformed and plain-clothed -- blocked off roads around the court again on Friday morning, with the only journalists able to gain entry to the proceedings from state-run media.

A convoy thought to be carrying Bo, which included a silver Mercedes prison van, pulled into the main entrance shortly before the trial restarted in the morning.