It is doubtful professional cold case investigators, no matter what evidence they might find, could ever solve irrefutably a probable murder more than half a millennium ago. Absolutely nothing—not even an indisputably authenticated confession by his successor on the throne--would be enough to absolve Richard III, King of England, from the accepted popular assumption he arranged the murder of his two nephews in the Tower of London.
This was foretold sadly by Scotland Yard's Alan Grant in 1951 after his exhaustive probe into historical records pointed the accusing finger instead at Henry VII. Grant is a fictional character, but this matters not in the least. The evidence he and his fictional assistants dug up were found in nonfictional records by his creator, Scottish playwright/novelist Elizabeth MacIntosh, while researching a play set in that period. Under the nom de plume Josephine Tey she devoted the fifth in her series of Inspector Grant mysteries to perhaps England's oldest and most controversial real murder mysteries, known down the ages as The Princes in the Tower.