Former UBS trader Kweku Adoboli will start telling his side of the story in court on Thursday, seeking to convince a jury that he did not act dishonestly when he made the trades that cost the Swiss bank $2.3 billion.
After listening quietly from the back of the London courtroom for six weeks as one after another of his former UBS colleagues took the witness stand, Adoboli is expected to begin giving evidence during the course of Thursday's hearing.
It will be the first time the 11 jurors hear the voice of the 32-year-old, British-educated Ghanaian, who used to work as a senior trader on the Exchange Traded Funds (ETFs) desk.
Adoboli was arrested at UBS's London offices in the middle of the night on September 15, 2011, hours after he sent an email to a back-office accountant explaining that he had booked fictitious trades to conceal losses made on "off-book" trades.
He has pleaded not guilty to two charges of fraud by abuse of position and two of false accounting. The charges cover two periods, from October 2008 to the end of May 2011, and from May 31 to September 15, 2011.
Under British law, the prosecution must prove not only that Adoboli's actions amounted to fraud and false accounting but also that his intentions were dishonest.
Adoboli's evidence will begin with questions from his own counsel, then he will be cross-examined by the prosecution.
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The lawyers estimated beforehand that the entire process could take three days, although previous time estimates given in the trial have turned out to be short of the mark.
UBS standards scrutinised
Prosecutors have portrayed Adoboli as a greedy, out-of-control rogue trader who recklessly gambled away UBS's money because he wanted to be a star of the trading floor and earn bigger bonuses.
They have described a "pyramid of fraud" in which he routinely exceeded his risk limits, concealed his positions by booking fictitious hedges and lied to the back office when asked questions about his trades.
In their cross-examination of the prosecution witnesses, the defence team have sought to show that others within UBS knew of and condoned some of Adoboli's methods, particularly his so-called umbrella.
This was an accounting mechanism he used to keep some of the profits from his unauthorised trades out of the desk's profit and loss accounts and then to drip-feed them back into the accounts to smoothe out fluctuations.
They have also tried to demonstrate that supervision of the ETF desk was inadequate, risk management systems sloppy, back-office staff complacent and chains of command unclear.
The defence have suggested that Adoboli was acting for the good of the bank, in line with management calls for greater risk-taking in pursuit of greater profits.
They have said that if Adoboli's trades had resulted in profits rather than losses he would not have got in trouble.
The long-running trial has been a public relations headache for UBS. The bank is not a party, which means that under Britain's strict laws against prejudicing trials it is not allowed to comment publicly on evidence heard in court.
UBS has had to remain silent while Adoboli's defence team have spent weeks highlighting evidence that they say reflects poorly on the bank's standards and practices.
After Adoboli's evidence will come closing speeches from the prosecution and from the defence, then the judge's summing up. Then the jury will retire to consider their verdict.