Miranda rights are the legal instrument that maintains human rights when a clash between the individual and the authorities occur on criminal grounds. the obligation to issue a Miranda warning preserve the freedom of the private citizen from being arrested and charged on the whim of a law officer.
We all saw in the movies and on TV on crime shows, police officers reading people they arrest the following sentences:
You have the right to remain silent.
Everything you say can be used against you in court
You have the right for a lawyer . etc,
There are cases in the united states where criminals were sent free (and I am talking about dangerous criminals) only because they had not been read their Miranda Rights.
It may sound outrageous to hear about a criminal who walks free, but you have to remember that these are the exceptional cases. In most cases it is the innocent citizen that must be protected against the excessive use of power by the authorities.