“I deny the allegations. I was not involved in a criminal conspiracy,” Kelly said.

Ghosn a fugitive or victim? The issue that split Japan into locals and foreigners

The trial, expected to last around 10 months, centres around the question of whether Kelly and Nissan illegally concealed payments between 2010 and 2018 of around 9.2 billion yen (US$87 million at today’s rates) promised to Ghosn on retirement.

Nissan, which is on trial alongside Kelly, says they did, and pleaded guilty to the charge against it on Tuesday.

Kelly, who turned 64 on Tuesday, entered the court dressed in a dark suit and red striped tie and wearing a surgical mask. He declined to speak to media gathered outside for the trial.

Inside the courtroom, he described Ghosn as an “extraordinary executive” who brought Nissan back from the brink of bankruptcy and was considered a “retention risk” because rules introduced in Japan from 2010 limited executive pay.

He said various options for additional pay to Ghosn were considered, and he “took it for granted” that any compensation would be “lawful”.

“The evidence will show I did not break the law,” Kelly added.

Did Ghosn flee Japan in a musical instrument box?

Nissan and Japanese prosecutors disagree, arguing they have evidence that future payments were pledged to Ghosn and therefore should have been disclosed in the firm’s financial filings as required by Japanese law.

Prosecutors have amassed a vast trove of documents, only a small portion of which the defence have been given so far, according to Kelly’s lawyers.

His defence team said they agreed to move to trial despite that, arguing they had “no choice” because Kelly – who has been out on bail in Tokyo since December 2018 – is separated from most of his family while he waits for his case to go to court.

His wife Dee has stayed in Tokyo with him and told reporters it was “disappointing” that Ghosn would not be testifying.

“But he is not here and he made the choice and he had to make that choice,” she said. “He is going to have to deal with the consequences of the choice he made.”

Family of Nissan’s Greg Kelly petition US to pressure Japan for his release

Kelly’s legal team say they are confident he can be acquitted – despite the track record of Japan’s prosecutors, who win over 99 per cent of the criminal cases they bring to court.

But they argue they have been put at a strong disadvantage by the court’s refusal to allow overseas witnesses to testify by videoconference.

Nissan has been tight-lipped about the trial, with a source close to the firm’s leadership saying there was concern about negative media attention.

The witness list includes a number of top former or current Nissan executives, including Kelly’s former colleague Hari Nada, who obtained whistle-blower status from prosecutors in exchange for his cooperation.

Former CEO Hiroto Saikawa, who was forced out over financial improprieties discovered by an internal investigation in the wake of the Ghosn scandal, will also give testimony.