The jury in the trial of Kweku Adoboli, the former UBS trader accused of causing the largest unauthorized trading loss in British history, began deliberations on whether or not he is guilty.

The 11-person jury was sent out at 2:30 p.m. yesterday to consider two counts of fraud and four false accounting charges. He has been on trial since 14th Sept., one year after he confessed in an e-mail to a UBS accountant to booking fake hedges to hide the risk of his actions. The trades led to a $2.3 billion loss.

Adoboli testified before the London criminal court that his managers pressured him to take on more risk and overlooked the fact that the profits the desk was generating didn’t match up to its reported risk profile. He said nothing he did was dishonest and it was all intended to make money for the bank.

Jurors in the trial against Kweku Adoboli were told by the judge today to be cautious about evidence given by a key witness, John Hughes.

Adoboli faces two charges of fraud and four of false accounting in a case that saw UBS lose $2.3 billion in September 2011.

In his final day of summing up, Judge Brian Keith warned jurors that Hughes may have had his own agenda when giving evidence in court. "It would be wise for you to treat John Hughes's evidence on the umbrella and other areas of the case with caution, as he may have his own reasons to address these issues," Keith said.

The umbrella refers to the account set up by Adoboli to conceal the profits and losses he made from unauthorised trades. Hughes was fired from UBS in the light of the trading losses.

Judge Keith also told jurors they must carefully consider the evidence relating to how much UBS management, the back office and fellow traders knew about the umbrella account and Adoboli's trading.

"This represents an important part of Adoboli's case, because he says he wasn't secretive about what he was doing as he felt he wasn't being dishonest. Adoboli says he felt comfortable that it was on people's radar as this showed him he wasn't being dishonest," Keith told jurors.

Adoboli's defence claims the UBS management knew of his actions – a point disputed by the prosecution. This issue is important, Judge Keith said.

"If all of these [people] knew he was amassing huge positions on unhedged trades and were turning a blind eye, then that's one thing. But if those trades were only known to fellow traders and the back office, then the prosecution say those people may themselves also be culpable, but this doesn't mean Adoboli was being honest."

Jurors were also asked to consider evidence regarding an email about Jérôme Kerviel – the trader convicted of losing French bank Société Générale €4.9 billion in 2008. During the course of Adoboli's trial, the court heard that UBS had sent a global compliance alert in January 2008 about the Kerviel case. Judge Keith reminded the court of an email exchange between Adoboli and a friend, in which they had joked about Kerviel's defence of burnout – a defence that Adoboli would come to present himself during his own trial.

"Trading is stressful and burnout is a phenomenon in this industry," Judge Keith told jurors. "There can be incidents of burnout that could lead to behaviour that might be seen as dishonest without the perpetrator realising he is acting dishonestly."

However, he reminded the court that while Adoboli claimed he was under massive stress, which led to his trades spiralling out of control, there was no psychiatric evidence to suggest he was suffering from burnout.

The jury has now retired to consider its verdicts on all six counts.