Hint: when someone explains a case in a way that uses absolutes to describe unknowable states of mind ("no doubt he was exercising his Fifth Amendment privilege"), stop reading the explanation and go read the case:
https://www.bloomberglaw.com/public/desktop/document/SALINAS....
It is well settled that the Fifth Amendment right against self-incrimination must be explicitly invoked:
> The privilege against self-incrimination "is an exception to the general principle that the Government has the right to everyone's testimony." Garner v. United States, 424 U. S. 648, 658, n. 11 (1976). To prevent the privilege from shielding information not properly within its scope, we have long held that a witness who "`desires the protection of the privilege . . . must claim it'" at the time he relies on it. Murphy, 465 U. S., at 427 (quoting Monia, 317 U. S., at 427). See also United States ex rel. Vajtauer v. Commissioner of Immigration[384] , 273 U. S. 103, 113 (1927).
> That requirement ensures that the Government is put on notice when a witness intends to rely on the privilege so that it may either argue that the testimony sought could not be self-incriminating, see Hoffman v. United States, 341 U. S. 479, 486 (1951), or cure any potential self-incrimination through a grant of immunity, see Kastigar v. United States, 406 U. S. 441, 448 (1972). The express invocation requirement also gives courts tasked with evaluating a Fifth Amendment claim a contemporaneous record establishing the witness' reasons for refusing to answer. See Roberts v. United States, 445 U. S. 552, 560, n. 7 (1980) ("A witness may not employ the privilege to avoid giving testimony that he simply would prefer not to give"); Hutcheson v. United States, 369 U. S. 599, 610-611 (1962) (declining to treat invocation of due process as proper assertion of the privilege). In these ways, insisting that witnesses expressly invoke the privilege "assures that the Government obtains all the information to which it is entitled." Garner, supra, at 658, n. 11.
In this case, the defendant had not been read Miranda warnings because he had not been taken into custody. It was a voluntary questioning. He then started answering questions, but went silent when talking about the ballistics evidence. Thus, the whole case was about whether "he was exercising his Fifth Amendment privilege" or not. The Court decided that under the circumstances, he was not:
> Petitioner 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 dissent elides this point when it cites our precedents in this area for the proposition that "[c]ircumstances, rather than explicit invocation, trigger the protection of the Fifth Amendment." Post, at 7-8 (opinion of BREYER, J.). The critical question is whether, under the "circumstances" of this case, petitioner was deprived of the ability to voluntarily invoke the Fifth Amendment. He was not.