Ciaran Maclochainn was released from the high security Maghaberry prison in Co Antrim and was taken to the Guildhall in Derry by his solicitor.
He is expected to tell the tribunal that he was with his friend Gerry Donaghy who was shot dead on Bloody Sunday and there was no way he could have been carrying nail bombs.
The body of Mr Donaghy, a member of the IRA’s youth wing, was later photographed with four nail bombs sticking out of his pockets.
His family contest claims that he was carrying devices on Bloody Sunday and insist they were planted on his body by members of the security services.
Meanwhile, journalists Alex Thomson and Lena Ferguson were expected to defend their right to protect their sources when they were recalled to give evidence to the inquiry.
The pair risked jail after refusing to reveal the identity of confidential sources when giving evidence in May 2002.
The television reports included claims that some of the dead and injured had been struck by bullets fired from the city’s walls.
On May 2, 2002, they were warned by tribunal chairman Lord Saville that he would have no option but to certify them for contempt to the High Court after they refused to reveal the identities of soldiers they had interviewed.
Ms Ferguson, who is now head of political programming at BBC Northern Ireland, was Mr Thomson’s producer at Channel 4 News when they interviewed five soldiers for a series of reports coinciding with the 25th anniversary of Bloody Sunday in January 1997.
When they gave evidence two years ago, the two journalists agreed to go back to the soldiers and seek permission to reveal their names.
One of the soldiers, known as B, was already known the inquiry.
Soldiers D and E released the two journalists from their duty of confidentiality, while A and C’s names have still not been made available to the inquiry.
Ms Ferguson was asked by counsel to the inquiry, Christopher Clarke QC, whether she had approached A and C.
She said she had been unable to make contact with either of them.
She was also asked about meetings with postgraduate student Paul Mahon, who was carrying out research into the events of January 30, 1972.
Ms Ferguson said she had met Mr Mahon twice in London.
She played him interviews with four of the soldiers they had questioned for the programmes.
She told the inquiry that she had not revealed to Mr Mahon the identities of any of the soldiers.
“My agreement with him was that he could hear my interviews with the soldiers, but I had stressed to him that because the soldiers were not to be identified, he was to respect the fact that I had this confidential agreement with them,” she said.
Mr Mahon supplied recordings of the interviews to the inquiry.
Ms Ferguson said she had no recollection of letting Mr Mahon record the interviews. Mr Thomson, the chief correspondent of Channel 4 News, described Mr Mahon’s actions as “an appalling and grotesque breach of trust”.