When does the requirement to inform a suspect of their rights apply?

The requirement to inform a suspect of their rights applies during custodial interrogations because this is the point at which an individual is both in custody and subject to questioning by law enforcement. The landmark Supreme Court case Miranda v. Arizona established that suspects must be notified of their rights, including the right to remain silent and the right to an attorney, when they are in a situation where their freedom of movement is restricted and they are being interrogated. This is crucial to ensure that any statements made by the suspect are made voluntarily and with full awareness of their rights, thereby protecting against self-incrimination.

The other scenarios described do not trigger the requirement for Miranda warnings. For example, the rights do not need to be read during a trial, nor is it necessary when a suspect simply asks for an attorney outside of interrogation circumstances. Additionally, informing a suspect of their rights after a plea is entered doesn't align with the rationale behind the Miranda warnings, which are intended to protect rights during the investigative process prior to formal proceedings.