A jury at Dublin Circuit Criminal Court has heard that former Dublin solicitor Thomas Byrne forged documents to pretend he owned his clients' houses in order to borrow millions of euro from banks.

Prosecuting counsel  Remy Farrell said in some cases Mr Byrne took out multiple mortgages on clients' properties.

The court was told clients discovered their houses had been mortgaged after the Law Society took control of Mr Byrne's practice.

Mr Farrell said one of the more "distasteful aspects of the case" was that many of the clients were elderly ladies.

Mr Byrne has gone on trial charged with 51 theft, deception, fraud and forgery offences involving six banks and 12 properties in Dublin.

The 47-year-old from Mountjoy Square in Dublin has pleaded not guilty to the charges.

Mr Farrell said the case was essentially a fraud case, one of the largest to come before the court this year. It would involve a lot of documentary evidence.

However, he said it would not be a feat of endurance or memory marathon for the jury.

While there would be detailed documentary evidence, it was not the case that white collar crime such as this could not be dealt with or understood by a jury, he said.

The offences are alleged to have occurred between 2002 and 2007 at the "very zenith of the Celtic Tiger", Mr Farrell said.

He said it was during a time when large amounts of money were being loaned by banks on flimsy paperwork.

They were very different times to recent years and the jury members would find themselves considering the phrase "the past is a foreign country" throughout the trial.

He told the jury it could expect to hear a lot of evidence about the law on buying and selling houses, stamp duty and deeds of transfer.

Mr Farrell said not only had Mr Byrne forged deeds of transfer, but he spent significant amounts of his own money having them officially stamped so he could use them to borrow money from the banks.

Many of the witnesses in the case were former friends and clients of Mr Byrne, he said. He had grown up in the area of Walkinstown where he later set up his legal practice.

Mr Farrell said on one occasion Mr Byrne told a client he had a buyer for her house, but the prosecution said the "mystery buyer" never existed because Mr Byrne "was spinning a yarn to buy time" after he had forged documents to say the client had sold the house to him.

He said a lot of circumstantial evidence would be produced. This was not a lesser form of evidence, it was one of the strongest, he said.

Mr Farrell said even if the jury could not have direct evidence that Mr Byrne forged documents, they could be sure he was in on it and therefore responsible in law.

The trial is expected to last up to eight weeks.