There is no "author" per se. Blackstone wrote about it in his Commentaries.
It is better that ten guilty persons escape than that one innocent suffer
Crucially Blackstone's achievement was summarising the common law into a single body of work. By default it is derivative; i.e. expressing what every lawyer in the country knew at the time. Blackstone's ratio is no different; it is an axiom of English common law which pre-existed even Blackstone but was expounded by Blackstone in his Commentaries.
It is a justification for a high standard of proof in criminal prosecutions. A high standard ensures no one is wrongly convicted but also means that people who are guilty will walk free as the evidence provided will not meet the high standard. The justification for this is the ratio.