A libertarian blogger made a few very good points.
Now, anything you don't say can and will be used against you. (My favorite rhetorical comment.)
Regarding mere silence without an express invocation of the right, what if the cops don't read a fella his rights? If he doesn't already know them, he won't invoke them. If he doesn't invoke this so-called fighting right, he's outa luck.
If government can use your sudden silence mid-questioning against you, its only one short step to using your invocation of the right against you.
I would add something I just remembered from the history of the 5th Amendment right against self-incrimination. The very foundation of the right is conscience and self-preservation. In the 1500's and 1600's multiple proponents of the right correctly identified compulsory self-incrimination as a form of torture, meaning a mental torture, anguish. Don't sell this short. Imagine your worst non-criminal sin--I use the word sin in its non-religious sense. Then imagine having to confess that. The mental resistance can be very, very strong, literally overwhelming to the point a person cannot move his mouth and tongue. Now, recall having done something of which you were particularly unproud--something not necessarily criminal but really wrong--but thought was undiscovered, and the terror when it was discovered. Recall the terror of when something was just strongly suspected, for example by a spouse or parent. So, yes, I can completely understand and agree that compulsory self-incrimination is mental torture. I have no problem at all accepting that, and consider it axiomatic.
So, for Salinas to go silent when the cop turned to the ballistics question, plainly showing a specific suspicion in Salinas, I can totally understand Salinas going silent, especially if he's guilty. Now, one might think, "great, he's guilty; he should be punished." But, don't forget the same principle of silence = guilt can be applied by government to malum prohibitum offenses (offenses that are offenses just because the government says they are, not because they are wrong in and of themselves.) That was how the hell we got the right in the first place--government punishing people because they were suspected of doing things that were objectionable to government, not because the offense was wrong in its own right.
The principle of silence = guilt can also be applied to people who are poor debaters when a cop asks a particularly dastardly question. For example, the cops asks an innocent suspect, "How did the shotgun shells at the scene match the firing pin on your shotgun?" Take a few seconds too long to figure out an answer, and months later at trial, the cop testifies not that the suspect didn't have an answer but that, "The defendant became silent."
No, no, no. Rights are rights are rights are rights. And, this particular right was far too expensive to obtain to tolerate even the tiniest infringement by government. On the way to obtaining this right, numerous people were convicted of not conforming to government-mandated ideas in Tudor England, and then turned out of their job, or heavily fined. Four men had their ears cut-off--one had already suffered that punishment, but the court saw stumps of ears and had those cut off. At least one was branded on the face. Queen Mary Tudor (Bloody Mary), daughter of Henry VIII burned at the stake almost 300 people. John Lilburne was whipped a walking mile, at the end of which he was pilloried; and, when he continued his pro-freedom speech from the pillory, the guard captain had him gagged so tight his jaws bled. He spent most of his adult life in prison, his health finally being broken to die in his early forties.
This right was literally paid for in blood and smoke. Literally. No backing up should be tolerated. Even so much as a government sigh indicating it wished it could infringe should be met with outrage and brandished pitchforks.