Belfast Crown Court Judge Corinne Philpott QC said she had no doubt that Conor Casey, 41, knew there would be gunmen at the funeral and that he lifted the spent cartridges "so that no information as to the likely provenance of the ammunition would be found".
The Deputy Recorder of Belfast said while the case "clearly" meets the custody threshold, Casey was "clearly a friend of Mr Brady who assisted him to deal with custody when convicted of the explosives offence".
In October 2002, Casey was jailed for 14 years after he was caught red-handed with a 200lb car bomb in the previous November.
Dressed in a boiler suit with body armour underneath, Casey had to be dragged from his white Vauxhall Astra car after being stopped at a police check point at Knappagh Road, near Killylea in Co Armagh.
When the vehicle was searched, police uncovered a two-way radio and a trigger mechanism for the massive bomb which was primed and ready for use.
Casey - whose father Tommy, a member of Sinn Féin, was murdered by loyalists in 1990 aged 57 - was released on licence in November 2008, but took part in Mr Brady's funeral in October 2009 at the request of the deceased's daughter.
In 1989, Brady was jailed for the murder of a policeman and the pair became friends when they shared a cell.
But, the former IRA man was found lifeless in a police cell in 2009. He had died by suicide.
Casey from Forth Glen, Cookstown, is currently on licence until 2015 for the explosives offences and last month, he pleaded guilty to assisting in arranging, or managing a meeting, knowing it was in support of a proscribed organisation, and aiding and abetting the possession of a gun and ammunition under suspicious circumstances.
He was charged in relation to the funeral after video footage was put on YouTube which showed Casey, dressed in white shirt and black tie, as one of four men who went into Brady's house and returned back outside with the gunmen.
After they fired a volley of shots over the coffin, Casey can be seen bending down to pick up the spent cases.
Judge Philpott said she was taking into account the fact that the charges had been hanging over Casey's head for a lengthy period, his mental health difficulties, his guilty plea and that he aided and abetted the possession of firearms.
In suspending the term for three years, she added that in effect, as he will be on licence for another two years, he will have another year of supervision added to that.