""People should only be in prison where guilt is proved beyond reasonable doubt""

And, there is a legal system in most western countries to deal with that. You are considered innocent until proven guilty. Once you have been determined guilty, there are appeals systems (based on the trial and any admissable new facts). However, once you are found guilty, legally proving you are not guilty is very complex,and an up hill battle (made more difficult with time).

Beyond that, there are personal opinions, books, movies, magazines articles, petitions, web articles, songs (etc) to try and sway public opinion. But, in the end, it is not up to public opinion, it all comes back to the codified legal system in each country.

Whether one feels the law is fair oe not, likely depends on the side of an issue your interests/sympathies lie, an assesment of facts (logical and biased, or less so)and of course your personal opinion.