Yes, there are some who are innocent.
The justice system is not perfect, it is human.
Some police and lawyers operate more by suspicion or opinion than fact.
D.A.'s often want to get a conviction more than discover the real truth.
At various times in life I have thought there ought to be a 3rd lawyer in courts who is tasked not with the defense or the prosecution, but with uncovering the true facts. An Advocate for the Truth.
But I am not a lawyer, nor a criminal.
I am a person who does not like to see innocent punished for guilty, a real concern, and think more so in my case than for the average person.
I am more scientist and like to judge things based on facts.
Three times summoned for jury service and both lawyers turned me down flatly. You know why? Because each one is looking for jurors who could be convinced to go his way. They are not looking for scientific nerd who goes by facts.
But I value "innocent until proven guilty"
As for the 5th, I think the Founding Fathers did not want it made possible to coerce a person into incriminating himself. Because police in many countries do use force to extract confession. Even if you are innocent, once that has been done, the victim of it is usually a goner. Iran still does this diligently. They also use it to convict anyone the 'political' leaders do not like.
If self-incrimination were allowed, yes, some guilty would be punished. But police would likely go hog wild over time and more and more innocent would be convicted. But in the USA, so far, 5th has mostly been pleaded by the guilty or criminals who have matters to hide.
Law enforcement, police and lawyers are more diligent in some states and less so in others. Occasionally there are too many who are lazy involved. So the fairness varies from state to state, and sometimes within a state and over time depending on the people who are involved with the justice in that case.
But the worst is not being able to admit mistakes. That has improved a little bit of late, and some innocent have been allowed to go free after many years in prison.
Early in my long life there was little chance for the innocent to ever be released, especially 1950--1980. Talking about USA here.
No system can be free fom error until there is feedback, evaluation of quality of outcome, study and monitoring. Scientific fact. A tiny growth of that has started in the last 30 years, but it is still done mostly by unpaid, non-profit and conscientious groups.
Most prisoners ARE guilty. I would discount much that they do or say when incriminating others, especially where they receive favorable consideration for shorter sentences.
Plea bargaining is often used by the lazy or to conserve funds for investigating more thoroughly. Of all the things lawyers do, I detest plea bargaining the most.
I do not know whether that is because I am scientist or Christian.
The justice system is very good and fair (in the USA) overall. But it is definitely NOT perfect. And some terrible miscarriages of justice do occur from time rto time.
Also the guilty going free in additions to the innocent being imprisoned.
In one way I am liberal to conservative views. I do not think anyone should be totally FORGOTTEN. Not even guilty prisoners. What I mean by that is that we all should know what the prison conditions are, and check them out periodically. No sadists or sex maniacs involved with correctional personnel duties. No drugs. No unnecessary and gratuitous cruel procedures.
I would have at least three types of prisons too. Some criminals are not too bad, but some are quite awful and dangerous. The worst lifers and meanest types need separate places. A mild criminal should not have life at risk by being confined with them in same facility.
So I do approve of milder prison for non-violent types of criminals.
I saw one case where the innocent man imprisoned looked almost exactly like the true rapist who was caught later. But the innocent man was ID'd totally by the victims who had to apologize to him after years of incarceration.
But I do not claim to have all the best ideas on this. However, I do claim to be able to judge who might be eligible for parole MUCH MUCH MUCH better than virtually all who are serving in that capacity. Especially with serious cases.
BTW, that is another place where mistakes are made....
If the lawyer who had the biggest ego or the least ego about winning his case ends up losing -- is that justice being served? Would not justice be served best by discovering the truth? Rather than persuading jurors who have trouble making good judgments of fact.