The case against Thomas "Slab" Murphy is based on "utterly ludicrous" documentation which attempts to link the prominent republican to a non-existent farming income, his defence barrister has said.
The 66-year-old from Ballybinaby, Hackballscross, Co Louth, denies nine charges of tax evasion.
During a third day of closing submissions, Dublin's non-jury Special Criminal Court was told that "fair analysis" of the evidence should lead to the conclusion it was the accused's brother, Patrick Murphy, who ran the operation and controlled the finances.
John Kearney SC said: "I am suggesting that the person in charge of this farming enterprise was Patrick Murphy; that the profiteer was Patrick Murphy; that the chargeable person was Patrick Murphy.
"I am not suggesting that Thomas Murphy was not about the farm. But there is a big difference between growing up in a farming environment and being about the place doing bits and bobs and being the chargeable person, being the actual farmer in charge."
The charges relate to the alleged failure to comply with tax laws in the Irish Republic by not furnishing authorities with a return of income, profits or gains or the sources of them over eight years from 1996 to 2004.
The high profile law suit is being heard by a panel of three judges led by Mr Justice Paul Butler.
They were told the case has been built on hearsay evidence and that key financial documents found inside Patrick Murphy's house had effectively been "buried" because they "didn't suit".
"When you scratch below the surface the reasonable doubt lurks just below the surface and so does Patrick Murphy," he said.
It was also claimed the state was seeking to "galvanise" the suggestion Thomas Murphy received a farming income.
"It simply isn't there," the lawyer said.
The inclusion of "business drawings" for items like food, presents, watch repairs, boots and tickets to Paris should also deposit doubt in the minds of the judges, the barrister said.
"That's the height of the prosecution case. It reached the stage that it was utterly ludicrous," Mr Kearney said.
Allegations that Murphy had access to large sources of cash were also rejected.
During an court earlier hearing Paul Burns SC, for the state, said during the period in question Murphy applied for a "herd number for keeping cattle" - a registration issued to farmers.
Using the number, he applied for and received state grants from the Department of Agriculture totalling well over 100,000 euro (£73,000), he told the court.
Substantial cash payments were also made by the accused to rent land over the same period, as well as payments in relation to silage used on the rented lands, the barrister said.
Throughout the lengthy hearing Murphy, who was dressed in a pink open neck shirt, brown coat and dark green trousers, sat impassively.
A number of friends and relatives sat separately a short distance away.
The trial continues.