The justice system in America encompasses more than prisons, jails and courthouses. Parole situations, extradition policy, immigration policy, and so many more elements can enter into our discussion of this system of rules, policies, and the people who enforce those rules and policies.
Considering the rather high dergee of disagreement on certain national policies, it seems hard to imagine anyone saying that the system is always right. The system does not even always consider itself to be right, as in the current case of immigration policy.
Unable to pass positive legislation (the DREAM Act), the Obama administration resorted to a stoppage of enforcement of immigration regulation relating to certain specific demographics.
Anytime humans are involved, there is going to be human error and human flaws. There is no escaping that fact. Given that we live in a fallen, imperfect world, we still have to find our way to some kind of justice. The judicial system is balanced as well as it can be with judges and peers to ensure adherence to law as well as empathy under the law. Justice is supposed to be blind, which is certainly a high and unattainable standard. it is, however, the goal. If we have the right motives and a worthy goal, we're doing as well as we can expect--and better than most.
In The Crucible, the judicial system of the day was a blend of man's law and God's law. Obviously, it didn't work in this case because the spiritual matters took precedence over legal matters. No balance, no true justice.
Any justice system is flawed, and far from perfect in that it is designed and run by humans, and human motivations and relationships are themselves flawed. So a statement about the justice system always being right is actually absurd.
In terms of The Crucible, the justice system is powerful, and claims blessing by God and omnipotence in legal affairs, but that didn't make it "right", far from it.
Of course not. Historically, there wasn't even a "justice system" when the Witch Trials began; an interim court was established to hear evidence. However, what fueled much of the legal difficulty was the admittance of "spectral evidence." After several people were executed, the governor forbade any prosecution based upon that, and the whole nasty affair stopped short.
The long term effect of the trials, where judges were both religious and secular leaders, were to forever damage the theocratic government in Massachusetts, which eventually led to a purely secular government.
One of the most powerful elements to Miller's work is its belief that the justice system can make mistakes if individuals do not follow its prescribed rules and understandings. In Salem's case, Miller shows what happens when hearsay, gossip, and fear take place for substantial pieces of evidence that are meant to meet their prescribed standards in a court of law. Abigail's accusations strike at the heart of all paranoia in Salem, causing the townspeople to abandon all sense of legal and moral rationality and capitulate to their worst behaviors and fears. Miller's depiction of Salem's legal system is one where checks are disposed, procedure is dismissed, and individuals assert power through innuendo and intimidation. We are able to examine this legal system and conclude that this type of justice is wrong. Yet, the true talent of Miller's work lies in our own execution of justice and whether or not ours bears any similarity to theirs. In the final analysis, Miller's Salem is the oppositional force to which our brand of justice must strive against.
The obvious answer is "no." The justice system in America tries to do its best, but in the end no system is perfect. This is not a cheap shot at the American justice system, but just an acknowledgement that we live in a broken world. This is why there are some, who are wrongly accused. Others who are guilty, but never brought to a court of law due to money or influence. There is also racism. There are all factors that make any system imperfect.
Now if we relate this to Miller's Crucible, then injustices are underlined even more. The Crucible is about the Salem Witch Trials and how absurd they were. It was really a travesty of justice. Also this work is a microcosm of Miller's world. Miller lived during the McCarthy era, where there were modern day "witch hunts" for people who were deemed unamerican.
In light of this, I think part of the work show that when the government or people of influence have too much power, then there will be greater injustices.