Former MP Ivan Cooper, 75, still regards the fatal shootings in Londonderry on 30 January 1972 following a civil rights march with disbelief.
Thirteen died on the day, with 15 others shot and injured by soldiers from support company of the 1st Battalion Parachute Regiment.
All 13 victims were declared innocent in 2010 following a 10-year public inquiry conducted by Lord Saville.
Then-prime minister David Cameron issued a public apology to the families on behalf of the state following the report.
An investigation by the Police Service of Northern Ireland (PSNI) followed the £195 million inquiry and files were submitted to the Public Prosecution Service (PPS) in 2016 and 2017 for consideration.
On Thursday the PPS is set to announce whether it will pursue prosecutions against some or any of 20 suspects.
This number includes 18 soldiers, one of whom has since died, and two Official IRA suspects.
John Kelly, whose 17-year-old brother Michael was among those shot dead, said it is a day the families have been waiting for with great expectation after 47 years.
Mr Cooper, who was one of the civil rights leaders on the march that day, backed the families calling for prosecutions, saying that “murder is murder”.
Lord Ramsbotham, who was military assistant to the chief of the general staff at the time of Bloody Sunday, has warned against the step.
He said: “I hope that they are not prosecuted because it sets a very difficult precedent. It’s a very dangerous precedent.”
The question has seen Northern Ireland’s parties split.
Democratic Unionist MP Gregory Campbell also expressed concern about the sort of precedent it would set in terms of dealing with Northern Ireland’s troubled past.
Ulster Unionist MP and former soldier Doug Beattie said if there is evidence that individuals broke the law on that day then they should face the law, adding that “so should the IRA members present that day”.
Sinn Fein and the SDLP have backed calls for prosecutions.
While one of the injured died five months later in hospital, from an inoperable brain tumour, the Saville Report did not link his death to the wounds he sustained on Bloody Sunday.
Many view John Johnson as the 14th person who died as a result of the violence.
He was shot twice but his death was attributed to a brain tumour.