Kweku Adoboli was arrested last year and is charged with fraud and false accounting, for allegedly losing his bank, UBS, a cool $2.3 billion in so-called unauthorised trades.
The 32-year-old Ghanaian has pleaded not guilty to the charge.
On Friday the prosecution accused him of acting like a naked gambler.
At one level this is a trial about the misdeeds of a single rogue trader and how he was able to make such a mess of things for so long.
In the public’s perception at least, the behaviour of banks like UBS is at the heart of the ongoing economic crisis.
Al Jazeera's Sylvia Lennan reports.