If you want to invoke your constitutional right to remain silent, you’d better not be silent.

That’s the circular logic of a recent ruling by the U.S. Supreme Court, which held that simply remaining silent is not enough to protect American citizens from self-incrimination. Though it’s received scant media attention, the decision has serious implications for criminal prosecutions, legal experts say. It came on June 17 in Salinas v. Texas, which concerned the nature of police questioning in a 20-year-old murder investigation that led to the conviction of a Houston man.

In January 1993, Genovevo Salinas was brought in for police questioning about the murder of two brothers. Police found shotgun shell casings at the scene, and Salinas -- who was not arrested and not read his Miranda rights -- agreed to let police inspect his shotgun. When police asked if the shells would match his shotgun, Salinas did not answer the question. He stayed silent, looked down at the floor, shuffled his feet and bit his bottom lip.

Salinas was later arrested on an unrelated traffic warrant, at which time police decided there was enough evidence to charge him with the murders. Salinas did not testify at the trial, but his reaction to police questioning -- the fidgeting, lip-biting, etc. -- was used as evidence. In other words, Salinas’ silence was used against him, a violation of his Fifth Amendment rights, or so he thought.

Salinas was convicted and received a 20-year sentence. On direct appeal, he argued to the Court of Appeals of Texas that the prosecutors’ use of his silence as part of their case was unconstitutional, but the court rejected that argument. The case eventually made its way to the Supreme Court, where in a 5-4 decision last week, the court found that Salinas’ self-incrimination privilege had not been violated, mainly because he never flat-out said, “I’m invoking my right to remain silent.” This despite the fact that Salinas was not under arrest at the time of questioning, and was therefore not read his Miranda rights.

From the plurality opinion, written by Justice Samuel Alito:

“Petitioner [Salinas] cannot benefit from that principle because it is undisputed that his interview with police was voluntary. As petitioner himself acknowledges, he agreed to accompany the officers to the station and ‘was free to leave at any time during the interview.’ Brief for Petitioner 2 - 3 (internal quotation marks omitted). That places petitioner’s situation outside the scope of Miranda and other cases in which we have held that various forms of governmental coercion prevented defendants from voluntarily invoking the privilege.”

The Supreme Court had previously held that mere silence is not sufficient for a suspect to invoke his or her Fifth Amendment rights. The difference here is that Salinas was not a suspect at the time he went silent; he was merely a witness brought in for questioning.

Alito was joined in his opinion by Justice Anthony Kennedy and Chief Justice Roberts. While the ruling has been overshadowed by this week's Supreme Court’s decisions on affirmative action, the Voting Rights Act, the Defense of Marriage Act and Prop 8, it’s received its share of criticism in both journalistic and legal circles.

Erwin Chemerinsky, dean of First Amendment law at the University of California, Irvine School of Law,wrote on the ABA Journal Tuesday that criminal defense lawyers will now have to take extra care, advising their clients to explicitly speak up if they wish to remain silent. He added that the new ruling is also likely to cause unnecessary confusion.

“Constitutional protections should not be just for those who have legal training and know what they need to say to the police to invoke their rights,” Chemerinsky wrote. “From a common sense perspective, Salinas was penalized for exercising his constitutional right to remain silent in the face of police questioning. This should not be tolerated under the Fifth Amendment.”

Read the full syllabus for Salinas v Texas here.