New evidence is discovered & Oversights and errors are corrected
Thats what i personally think because new opinions have to be backed with evidence, while if a piece of evidence is lost or stolen, it doesn't change the arguments because even though it is lost or stolen, there ought to be copies of the original object, but im not sure about new technology being applied to evidence, but it can go either or, its a 50/50 because new technology can enhance historical discoveries, or find new ones, but applying new technology as evidence has to be backed up with facts as to why it should be applied