The Supreme Court’s conservative majority ruled today  that suspects being interrogated can only invoke their right to be silent if they say so explicitly—they can’t just remain silent. Justice Sonia Sotomayor, in a dissenting opinion, called the ruling a "substantial retreat from the protection against compelled self-incrimination that Miranda v. Arizona has long provided.” The Los Angeles Times explains :
In the past, the court has said the "burden rests on the government" to show that a crime suspect has "knowingly and intelligently waived" his rights.
But in a 5-4 decision Tuesday, the court said the suspect had the duty to invoke his rights. If he failed to do so, his later words can be used to convict him, the justices said.
The ruling comes in a case involving a murder suspect who, though read his Miranda rights, never said he would waive them. After three hours of interrogation, he offered a few monosyllabic responses that implicated him in the crime. The Supreme Court’s majority, in an opinion by Justice Anthony Kennedy, went beyond the case in question to hold that suspects, rather than having to explicitly agree to be interrogated, have to explicitly invoke their Miranda rights in order to halt questioning.
Sotomayor pointed out that requiring a suspect to speak in order to remain silent doesn’t really make sense:
Justice Sonia Sotomayor, the court's newest member, wrote a strongly worded dissent for the court's liberals, saying the majority's decision "turns Miranda upside down."
"Criminal suspects must now unambiguously invoke their right to remain silent — which counterintuitively, requires them to speak," she said. "At the same time, suspects will be legally presumed to have waived their rights even if they have given no clear expression of their intent to do so. Those results, in my view, find no basis in Miranda or our subsequent cases and are inconsistent with the fair-trial principles on which those precedents are grounded."
She also criticized the majority for going beyond the decision necessary for the specific case in order to make new and broader rules:
If, in the Court’s view, the Michigan court did not unreasonably apply our Miranda precedents in denying Thompkins relief, it should simply say so and reverse the Sixth Circuit’s judgment on that ground. “It is a fundamental rule of judicial restraint . . . that this Court will not reach constitutional questions in advance of the necessity of deciding them.” Three Affiliated Tribes of Fort Berthold Reservation v. Wold Engineering, P. C., 467 U. S. 138, 157 (1984).
Two disturbing habits of the Roberts Court are on display here: the tendency to ignore the common-sense practicalities faced by the person with the least power in a given situation; and the zeal for going beyond the narrow bounds of a given case  and carving out a whole new set of rules  not necessary to the resolution of the case before them.
It’s a perfect example of how the Roberts majority, while displaying remarkable ambivalence to the practical implications of its rulings, isn’t just calling “balls and strikes”—it’s going to bat for its own unprecedented agenda.