When evidence is used to prove guilt in a criminal case, that evidence needs to be valid. It's a basic tenet of the criminal justice system that prosecutors aren't supposed to fight simply to win, but to fight for justice. They're not supposed to cut corners on evidence, and if there is a problem with that evidence, they're required to tell the defense.
Thanks to our exposure to countless police procedurals and crime movies, most Americans are familiar with the rights extended to those brought in for questioning. Whether the scene features an individual being placed in a squad car or interviewed at a police station, the actor interrogated was informed of the right to remain silent. The safeguard against self-incrimination proffered by the Miranda rights is one that Hollywood has taught Americans from an early age.