An inquiry into an event that took place 30 years ago was always going to encounter a number of problems.
One bound to emerge was the frailty of the human mind and its tendency to lose facts, forget events and conversations and replace "real-time" images with memories of subsequent media footage.
This was highlighted by the first day of evidence from a former army commander who was in Londonderry on Bloody Sunday.
General Sir Robert Ford was Commander of Land Forces in the province when British soldiers opened fire on civilians at a civil rights march on 30 January 1972.
Thirteen people were killed and another died later.
On Tuesday, the inquiry learnt of the existence of a memo, signed by Sir Robert, in which he suggested a policy of shooting some rioters in order to restore law and order in Derry.
The former general is a well-spoken, dapper gentleman, as one would expect of a former army officer.
Undermining the army
Many of the 78-year-old's answers are detailed, peppered with the precision of Army speak expected of any member of the top brass.
But a majority of his responses open with "I have no recollection", "I do not recall" or "I must assume".
In the secret memo to his superior, dated 7 January 1972, Sir Robert says he is "coming to the conclusion that the minimum force necessary to achieve a restoration of law and order is to shoot selected ringleaders amongst the DYH (Derry Young Hooligans), after clear warnings have been issued".
He describes the DYH as "gangs of tough teenage youths... who have developed sophisticated tactics of brick and stone throwing, destruction and arson."
In the general's mind the army was "virtually incapable" against these gangs, who operated under the cover of snipers and "undermined" the soldiers' ability to deal with gunmen and bombers.
But he did not advocate killing the ringleaders.
Oral briefing
The idea, which he told the inquiry would have needed further thought and development, was to use a lower calibre ammunition "to incapacitate and cause less casualties".
Although the general's witness statement acknowledges that implementing these ideas would have meant a change in tactics and rules of engagement for the army, he still failed to remember the memo.
In fact, he told the inquiry he did not remember dictating, signing or sending the memo, although he did accept it was his dictation.
Sir Robert said he had always assumed he had orally briefed his superior, General Sir Harry Tuzo.
He was only reminded of the document after picking up a copy of it from the MoD in April or May 1998, the inquiry heard.
Later in the inquiry Sir Robert is likely to be asked about his movements on Bloody Sunday.
Television memories
He was the commanding officer who approved a plan to carry out a large number of arrests to prevent violence on the civil rights march.
He says his words of encouragement to his men, "Go on 1 Para, go and get them" were picked up by media microphones.
How much more he will be able to recall from his own experience of events remains to be seen.
In his statement, he says he was present at 'barrier 14' when the first shots - baton rounds - were fired at the crowd. He remembers stones being thrown by the crowd but little more.
"I cannot now summon up a reliable mental image of what I could see across barrier 14," his statement reads.
"I have seen far too much footage on video and television since the event and I believe that such recollection as I now have comes from what I have seen since."
Sir Robert is expected to give evidence over a two-week period as, in deference to his age, his sessions are only being held in the morning.