Dr Lets Pretorius was giving evidence in an application for bail pending an application for leave to appeal against his conviction on high treason and sentence of 30 year's imprisonment, 10 of them suspended.
His sons, Johan, Kobus and Wilhelm, were among the 19 Boeremag members sentenced to between 10 and 48 years' imprisonment for conspiring to overthrow the ANC government in the early 2000s.
"A sentence of 20 years is actually a death sentence for me," Pretorius told the court.
"I am 67 years old and will be 87 when I've served 20 years. By that time, chances are good that neither I nor my wife will still be alive.
"I honestly never expected such a severe sentence and did not make long-term provision for my wife's care.
"I know it can be argued that I was convicted of violent crimes, but I'm a political prisoner and I'm also white.
"If I look and listen to what happens to other white political prisoners … I know as an enemy of the state that my chances of getting parole are slim."
Pretorius, who was out on bail for nine years before being sentenced earlier this week, testified that he had always adhered to his bail conditions and had no plans to flee.
He had lost his lucrative private practice and farm when he was arrested and thereafter moved to Pretoria, but had continued practising as a medical doctor in the past decade, assisting other doctors, working in the emergency wards at hospitals and doing work for the Road Accident Fund.
"I cannot see how I can be regarded as a danger to society. I've devoted my whole life to helping people," he said.
Pretorius said he was his wife Minnie's personal physician, psychiatrist and soulmate.
He had nursed her through breast cancer and depression, and also acted as a surrogate father to his grandchildren.
According to Pretorius, his wife had experienced his sentencing as a great shock and was not doing well emotionally.
His own health was also not good and he needed back and heart surgery and dental work.
His back problems were the result of an injury he sustained while in custody, he said.
Pretorius said he and his sons Johan and Wilhelm were bosom buddies, and the hardest thing for him was when his son Kobus broke off all relations with his family because of "outside influences".
He said even though the R500 000 bail bond was in the name of a property company in which he no longer had an interest, his family trust still had an interest in the business and would be harmed if he fled.
Pretorius said he wanted to help his advocate prepare for an appeal and also needed to generate funds for an appeal as it was uncertain if Legal Aid SA would fund his appeal.
"I've been advised that I have a chance on appeal. I think it would be very unwise to even consider fleeing or not to adhere to my bail conditions," he said.
Pieter Luyt, for the state, argued that Pretorius was a flight risk because of the long sentence he faced.
"There's no reasonable prospect of success on appeal and it is highly unlikely that another court would impose a different sentence.
"Through his crimes and his conduct, he [Pretorius] has clearly shown that he is a danger to society," Luyt argued.
Judge Eben Jordaan will deliver judgment in the bail application on Wednesday.
On Friday, the judge declared all the Boeremag members, except for Adriaan van Wyk and former defence force officers Giel Burger and Pieter van Deventer, unfit to possess firearms.
He ordered the police to search the homes of the accused and to confiscate all firearms, ammunition and related documents in their possession.
The three who were allowed to retain their firearm licences received suspended sentences because of their limited role in the coup plot.
Jordaan accepted their submissions that they needed their firearms for their work on farms and at a security company. – Sapa