There's a category of evidence in criminal cases called "consciousness-of-guilt" evidence. Guilty people do things an innocent person wouldn't. Examples include flight from police, changing physical appearance to thwart identification, and threatening or bribing witnesses.

Conduct that tends to indicate guilt is usually admissible in court, allowing the jury to draw the inference that the defendant's course of action shows that he is conscious of his own guilt and of the need to try to cover it up.

Therefore, whenever you see or hear a suspect doing or saying something an innocent person would not, your observations should go into your reports, so the prosecutor can evaluate the potential admissibility and evidentiary impact of the observed behavior. Even the suspect's selective silence can sometimes indicate a consciousness of guilt and might be admissible at trial, as the U.S. Supreme Court recently explained.

Salinas v. Texas

Two brothers were shotgunned to death in their Houston home. There were no witnesses, but a neighbor reported hearing the shots and seeing a man jump into a car and drive away. Officers recovered six shotgun shell casings at the scene.

Subsequent investigation led to a possible suspect, Genovevo Salinas. He agreed to accompany officers to the station for voluntary questioning, and his father turned over a shotgun to police.

At the station, it was made clear that Salinas was not under arrest and was free to leave at will. Officers questioned Salinas about his relationship to the brothers and his activities on the morning of the murders. Because this interrogation was not custodial, no Miranda warnings were given.

Salinas answered most of the questions, but when asked whether his shotgun would match the shells from the scene, he didn't reply. He made no response at all, much less one indicating he was asserting a constitutional right not to answer. Instead, he looked down at the floor, shuffled his feet, bit his bottom lip, clenched his hands in his lap, and "began to tighten up." He remained silent for a few moments, until the officer asked a different question, which Salinas then answered.

Following the interrogation, Salinas was arrested. At his subsequent murder trial, the prosecutor introduced evidence of Salinas's reaction to the ballistics question and argued that the failure to answer constituted evidence of a consciousness of guilt. The jury convicted, and Salinas was sentenced to 20 years in prison.

Required to Invoke the Fifth

On appeal to the U.S. Supreme Court, Salinas maintained that prosecutorial use of his silence violated the Fifth Amendment by penalizing his exercise of a constitutional right. A five-member majority of the court rejected this argument and affirmed the convictions.

The court pointed out that "the Fifth Amendment guarantees that no one may be compelled in any criminal case to be a witness against himself; it does not establish an unqualified right to remain silent." In other words, the Fifth Amendment does not say that suspects always have a right of silence, in all settings and under all circumstances, that can be invoked by simply remaining silent. They merely have a right not to be compelled to make statements or answer questions. Since Salinas was not under any compulsion during his non-custodial interrogation, the Fifth Amendment did not automatically shield his silence from evidentiary use.

In the court's split opinion, three justices said that assuming there could be a Fifth Amendment privilege not to talk to police in non-custodial settings, the burden would be on the suspect to expressly invoke it (such as by saying something like "I'm not talking on constitutional grounds," or "I'm taking the Fifth," or "I want to remain silent," or "I stand on my rights not to talk," etc.). The plurality opinion said the following:

"Before Salinas could rely on the privilege against compelled self-incrimination, he was required to invoke it. It would have been a simple matter for him to say that he was not answering the officer's question on Fifth Amendment grounds. Because he failed to do so, the prosecution's use of his non-custodial silence did not violate the Fifth Amendment."

In their concurring decision, two additional justices said they would go further and hold that there is no Fifth Amendment privilege to be invoked during non-custodial questioning because that privilege relates only to "compelled" self-incrimination; in the absence of custodial interrogation or some other form of compulsion that results in "testimony," the Fifth Amendment is inapplicable. These two justices said the following:

"In our view, Salinas's claim would fail even if he had invoked the privilege because the prosecutor's comments regarding the precustodial silence did not compel him to give self-incriminating testimony."

Although the two concurring opinions in Salinas differed somewhat, there were five votes—and thus a majority ruling—holding that a prosecutor can use silence against a defendant, at least absent express invocation of the Fifth Amendment, when that silence occurs during non-custodial police interrogation without Miranda warnings.

Miranda and Doyle

What is the significance of the fact that Salinas had not been given a gratuitous Miranda warning? When you Mirandize someone, you're telling him he has a right to remain silent. If he then invokes that right the prosecutor cannot use his silence against him because you induced his silence by giving the warning, and it would be unfair to extend a right to him and then penalize his exercise of that right. This is why you are not allowed to offer testimony in a jury trial to the effect that a suspect invoked after warnings. The Miranda decision itself said so:

"It is impermissible to penalize an individual for exercising his Fifth Amendment privilege when he is under police custodial interrogation. The prosecution may not use at trial the fact that he stood mute or claimed his privilege in the face of custodial accusation."

Also, the prosecutor is not allowed to use Miranda-induced silence to impeach a defendant's trial testimony. "While it is true that the Miranda warnings contain no express assurance that silence will carry no penalty, such assurance is implicit to any person who receives the warnings. In such circumstances, it would be fundamentally unfair and a deprivation of due process to allow the arrested person's silence to be used to impeach an explanation subsequently offered at trial." (Doyle v. Ohio)

By contrast, the Supreme Court has said that a suspect's silence before warnings have been given may be used against him because it has not been induced by official assurance that the suspect may remain silent. (Jenkins v. Anderson; Fletcher v. Weir)

Don't Over-Mirandize

In addition to the fact that Miranda warnings may prompt a person to clam up, these cases provide another reason not to give warnings when they aren't legally needed.

Although Hollywood screenwriters seem to think that Mirandizing suspects immediately upon arrest is standard police procedure, you and I know better. Premature warnings are unwise, and legally unnecessary.

If you Mirandize too soon—before the onset of custodial interrogation—you may deprive the prosecution of the ability to use the suspect's silence against him. Sometimes, silence can be very damaging evidence of a consciousness of guilt. Just ask Genovevo Salinas.

Devallis Rutledge is a former police officer and veteran prosecutor who currently serves as special counsel to the Los Angeles County district attorney. He is the author of 12 books, including "Investigative Constitutional Law."