Judge Patrick Lynch said the hearsay statements the prosecution case was "totally dependent upon" should be admitted, but it would be inappropriate at this point to give reasons for his decision.
A lawyer for the families of the victims, Ciaran Sheils, said on Wednesday they were "very, very pleased", describing the evidence as "decisive".
The trial would continue next week, with the prosecution case expected to take between two and four weeks, Belfast Crown Court heard.
Prosecutors initially decided in 2021 not to go to trial over fears that the statements given by two other soldiers, who were with the soldier charged over the killings in Londonderry on January 30, 1972, could be ruled inadmissible because of how the evidence was obtained.
Northern Ireland's High Court quashed the decision to discontinue the murder case in 2022 after a legal challenge by the victims' families and lawyers for the prosecution began presenting their case last week.
The soldier, who cannot be identified and is known as Soldier F, is accused of murdering two men and attempting to murder five others when members of Britain's Parachute Regiment opened fire in the mainly Irish nationalist city of Londonderry.
Soldier F has pleaded not guilty to the seven charges.
Bloody Sunday remains the worst single shooting incident of three decades of violence involving mainly Catholic nationalists seeking a united Ireland, largely Protestant pro-British unionists wanting to remain part of the United Kingdom and British forces.Â
A 1998 peace deal largely ended the bloodshed.
