'I pray for justice for my son,' says retired nurse Sammie Stanford

Allen Stanford's mother says she will not stop fighting to prove her son's prison beating left him too damaged to defend himself against fraud charges.

The 82-year-old retired nurse, Sammie Stanford, watched from the public gallery for the first time yesterday as her son's trial went into its fourth day, and said she would attend as much of the six-week hearing as her health would allow.

Speaking to The Independent, she gave an emotional defence of her son, who spent a year recovering from injuries sustained from a fight in custody and from an addiction to medicines prescribed by prison doctors. The Texan financier denies 14 counts of fraud, conspiracy and obstruction of regulators.

"I pray for justice," Mrs Stanford said. "I don't know about the ins and outs of the business, but I know my son."

Mr Stanford's lawyers had vainly argued that the effects of the prison beating had left him with permanent brain damage, including amnesia, which meant he was unable to assist them in preparing his defence – but last week Houston judge Dave Hittner ordered that Mr Stanford was fit to face trial.

Mrs Stanford said yesterday that she was continuing her efforts to reveal the extent of her son's injuries and was trying to find a new doctor to give an opinion on "before" and "after" brain scans. "I have maxed out my credit cards, I have taken a reverse mortgage on the house, and I have spent one-third of it on forensic experts, but none of it has done any good," she said.

Mr Stanford has been in custody since his arrest in 2009, having been judged a flight risk. His mother moved to North Carolina to be close to him as he recovered from his injuries at a prison system hospital there, and said she visited him almost every day. Now that the trial has begun she has returned to the Houston area, where she is staying with her daughter-in-law, Mr Stanford's estranged wife Susan, so that she can see him in court. "But I'm not even allowed to smile at him here," she said.

Mr Stanford is accused of running a $7bn pyramid scheme – with the exception of Bernard Madoff's, the largest in history – and duping thousands of investors all over the Americas. His Antiguan bank, it is alleged, made up phoney investment returns for more than two decades.

In its pomp, Stanford International Bank enabled its founder to live the life of an international playboy. In a television interview he boasted that "yes, it is fun being a billionaire", and showered millions of dollars of sponsorship money on English cricket. Approached by The Independent, Mrs Stanford asked: "You're not one of the ones that wrote nasty things about him and Twenty 20 cricket, are you?"

Mr Stanford's defence team says it will prove that Stanford International Bank's investments in Twenty20 cricket and other schemes were legitimate and potentially lucrative investments that were worth every penny Mr Stanford claimed.

Yesterday, the prosecution continued setting out its case, calling former Stanford employees to testify about the growth of the business in the 1990s.