For some reason, it only seems fair that people don't have to talk when they're in trouble with the law. Whether they're facing an inquisitive police officer or sitting in a courtroom, they shouldn't have to say something that could lead to a conviction. But it can be tough to put a finger on what, exactly, it is that makes the Fifth Amendment privilege against forced self-incrimination a good idea.
(For further information on this topic, see also Invoking Your Right to Remain Silent.)
Courts have explained that the privilege of silence is designed to avoid the "cruel trilemma" of perjury, contempt, and self-incrimination. In other words, someone who might have committed a crime and who is forced to answer questions about the conduct in question has to choose between:
Beyond the trilemma, courts have discussed three broader concepts underlying the Fifth Amendment.
Reliability. The theory is that compelled testimony is inherently unreliable. For example, an innocent person who can be forced to talk might confess for the simple goal of putting an end to an interrogation.
Coercion. The idea here is that law enforcement officers would use coercion, if not outright torture, if they knew that any admission they could extract would be admissible in court.
Adversarial system. Our legal system is founded on adversarial, rather than inquisitive, proceedings. That means that it's the government's burden, not the defendant's obligation, to provide evidence of guilt.