See the doctrine of circumstantial evidence is not a rigid principle. As opposed to direct evidence where witnesses depose as to what happenned - which is by it's very nature objective. In circumstantial evidence each fact or circumstance raises an inference - the inference of guilt or no guilt. Since it is inferential in nature, the person appreciating the evidence has an onerous responsibility. For eg : X was killed Y his friend is absconding after that. - Now a person may take this is an abscondence that is manifestive of guilty mind - Why should Y run away ? Is he guilty ? on the contrary another prudent man may take this to be as an innocent abscondence - the fear of wrongful implication + instinct of self survival - has ensured that even innocent people have fleed to escape arraignment. Hence it is too subjective - to introduce some objectivity or rather some consistent standards/safeguards the Supreme Court has over the years crystallised some principles, for eg :
1) All circumstances established conclusively;
2) All circumstances point towards the hypothesis of guilt, and hypothesis of innocense completely ruled out;
3) All circumstances forming a chain, so strong and complete that the story is reconstructed before the court ;
4) It appears that in all human probability accused committed the crime.
Even after this there is always subjectivity.
For people wronged by specific deicsion of the trial courts - who feel these principles have been disregarded - can appeal to the higher body.