Former Anglo Irish Bank chief executive David Drumm has pleaded not guilty at Dublin Circuit Criminal Court to being involved in an alleged €7.2bn conspiracy to defraud and to dishonestly furnishing false information to the market.
An extended jury panel of 15 people - seven women and eight men - has been sworn in to try him.
Judge Karen O'Connor strongly warned potential jurors not to research the case on the internet.
She also told them they should not serve if they held such strong views on Anglo Irish Bank that they did not feel they could deal with the matter fairly.
Speaking to potential jurors at the start of proceedings, Judge O'Connor warned them they should not sit on the jury if they were shareholders of Anglo Irish Bank, Irish Life and Permanent, Irish Life Investment Managers, or Irish Life Assurance, or were ever employed at those institutions.
Judge O'Connor said they should not sit on the jury if they had expressed views in public, on the internet or on social media on issues relating to Anglo, the banking crisis or bankers in general.
They should not serve, she said, if they knew anyone involved in the case or if they had ever worked for the Irish Financial Services Regulatory Authority, the Central Bank, the Department of Finance or any other body involved in the financial crisis.
She added that they should not serve if they were a qualified accountant or connected with accountancy firms EY or PWC.
Judge O'Connor also strongly warned the potential jurors not to research any aspect of the case online.
The judge said that material gleaned online could not be checked for veracity and reliability and it would be extremely dangerous to use such matters in this trial.
Judge O'Connor said that in a trial with such an enormous amount of material jurors might think it appropriate to research issues online, but she said this could lead to the trial collapsing, causing enormous expense and administrative difficulties.
She told them to decide the case based on what they heard in the courtroom alone and not to discuss it with anyone outside.
Mr Drumm, 51, from Skerries in Co Dublin, has pleaded not guilty to conspiring with Denis Casey, William McAteer, John Bowe and others to defraud, by engaging in transactions between Anglo, Irish Life and Permanent and Irish Life Assurance to mislead depositors, investors and lenders about the true value of deposits to Anglo between March and September 2008.
He has also denied furnishing false information to the market in December 2008, giving the impression that deposits from non-banks to Anglo were €7.2bn greater than they were.
The trial is expected to hear from almost 100 witnesses and could last up to five months.