Final answer:
It is the federal judiciary's responsibility, which includes the Supreme Court and lower federal courts, to ensure that states are following constitutional rights, especially in terms of upholding individual liberties and fair judicial processes.
Step-by-step explanation:
The question refers to the responsibility of ensuring that states are following constitutional rights in the context of the criminal justice system, as discussed in the book Just Mercy. This is primarily the role of the federal judiciary, which comprises the Supreme Court and lower federal courts. According to Article III of The Constitution, the judiciary has the power to interpret laws and assess whether state actions are in compliance with constitutional protections.
The Supreme Court can directly handle cases involving high-ranking officials or states themselves, as well as set legal precedents which affect the country's understanding and enforcement of individual rights. This court's decisions are crucial in ensuring equal justice under law, as highlighted by landmark cases that have affirmed the right to legal representation, fair trials, and protections against unfair punishment.
Furthermore, the Constitution outlines various individual rights and safeguards, such as the right to a trial by jury, protection against ex post facto laws, and the prohibition of bills of attainder. It is up to the judicial branch, a guardian of constitutionality and individual rights, to uphold these principles and ensure that federal and state actions do not infringe upon the personal freedoms guaranteed by the Constitution.