en.wikipedia.org/wiki/Miranda_warning

The Supreme Court has repeatedly described the Miranda rule as grounded in the Fifth Amendment privilege against self-incrimination. In Edwards v. Arizona, the Court stated that Miranda declared a Fifth and Fourteenth Amendment right to have counsel present during custodial interrogation. And official explanatory sources summarize Miranda as specifying procedures "in accordance with the Fifth Amendment" when police question a person in custody.

So while Miranda includes a right to counsel during custodial interrogation, that right is not described by the Court as a standalone Sixth Amendment basis for Miranda. The quoted bullet therefore misstates the doctrine.

This clause gets the Miranda warning requirement backwards. The Supreme Court's formulation in Miranda requires that, before questioning, a suspect be warned that they have the right to the presence of an attorney and, if indigent, appointed counsel prior to any questioning.

Later cases allow flexibility in exact phrasing, but not omission of the substance. In Florida v. Powell, the Court said Miranda requires that a suspect be "clearly informed" of "the right to consult with a lawyer and to have the lawyer with him during interrogation," and held that a warning about the right to talk to a lawyer before answering questions satisfied that requirement. So police do have to advise suspects of a pre-questioning right to counsel; they just need not use one rigid script.

Authoritative summaries of Miranda v. Arizona describe Ernesto Miranda as having been questioned in connection with kidnapping and rape, and the Arizona case summary says he was found guilty of kidnapping and rape. A separate Arizona case notes that robbery was charged in another information, i.e. a separate case. So describing the case as his arrest and trial for "armed robbery, kidnapping, and rape" is inaccurate.

The constitutional description is also off. Modern official summaries of Miranda describe the decision as requiring safeguards for the Fifth Amendment privilege against self-incrimination during custodial interrogation. Oyez's case summary says the majority concluded that Miranda's interrogation violated the Fifth Amendment. That contradicts the sentence's claim that the Court found both Fifth and Sixth Amendment rights violated in that case.

The Court's own explanations of Miranda describe it as a rule safeguarding the Fifth Amendment privilege against self-incrimination during custodial interrogation. In Edwards v. Arizona, the Supreme Court expressly summarized Miranda this way: "Miranda thus declared that an accused has a Fifth and Fourteenth Amendment right to have counsel present during custodial interrogation." That is directly inconsistent with saying Miranda held that admitting the statement violated the Sixth Amendment right to counsel.

Official summaries from Oyez and the Federal Judiciary say the same thing: the majority in Miranda concluded that the interrogation violated the Fifth Amendment, and that warnings are required to secure the privilege against self-incrimination. So the quoted phrase assigns the wrong constitutional source to the Miranda rule.

The quoted sentence conflates two different doctrines.

For custodial interrogation, the Supreme Court has said that the right to have counsel present is part of the Miranda safeguards protecting the Fifth Amendment privilege against self-incrimination. In Edwards v. Arizona, the Court stated: "Miranda thus declared that an accused has a Fifth and Fourteenth Amendment right to have counsel present during custodial interrogation."

By contrast, the Sixth Amendment right to counsel attaches only after adversarial judicial proceedings have begun—for example, by formal charge, preliminary hearing, indictment, information, or arraignment. The Constitution Annotated and Massiah materials describe the Sixth Amendment that way. So it is inaccurate to say that the Sixth Amendment right to counsel simply means a suspect may consult counsel before police questioning begins and have counsel present during interrogation.

This statement conflicts with Supreme Court precedent. In North Carolina v. Butler, the Court held that an express written or oral statement of waiver is not necessary to establish a valid Miranda waiver. And in Berghuis v. Thompkins, the Court reaffirmed that a waiver may be implied from a suspect's conduct and statements after receiving and understanding Miranda warnings.

So a waiver does not have to be "clear and unequivocal" in the sense of an explicit statement. What matters is whether the prosecution can show a knowing, intelligent, and voluntary waiver, which may be express or implied.