Why is knowledge inside one&#39;s head considered privileged information but knowledge written on a piece of paper is not?
<p>At least in the US, one can refuse to reveal information contained inside one's head by pleading the Fifth Amendment. However, the same protections don't apply to papers (or computer files) with information you might not want to share with the government. But why does this distinction exist at all? Why does the law make a distinction as to the medium in which certain information is contained?</p>

<p>The Fifth Amendment protection relates to a repugnant act, that of forcing a person to testify against themselves, and it is not about ways of looking at &quot;information&quot;. The relevant (legally-ancient) distinction is between a general inquiry and an accusation. The courts have always had the power to make a general inquiry, but there have been limits on the ability of the courts to make accusations. It is a fundamental requirement of law that there must be an accuser, if there is to be a criminal proceeding. But is it also considered to be morally repugnant to force a person to accuse themselves.</p>
<p>The difference lies not in the informational content in question, it is in what act – compelled self-accusation – is excluded from the legal system.</p>

<p>The relevant language of the Fifth Amendment is:</p>
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<p>No person ... shall be compelled in any criminal case to be a witness against himself.</p>
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<p>This Fifth Amendment privilege &quot;bars the State only from compelling 'communications' or 'testimony'&quot; (<em>South Dakota v. Neville</em>, <a href="https://tile.loc.gov/storage-services/service/ll/usrep/usrep459/usrep459553/usrep459553.pdf" rel="noreferrer">459 U.S. 553</a>, 559 (1983), citing <em>Schmerber v. California</em>, 384 U.S. 757 (1966)). The Court has also acknowledged the trouble you're noting: &quot;the distinction between real or physical evidence, on the one hand, and communications or testimony, on the other, is not readily drawn in many cases&quot; (<em>Neville</em>, p. 561).</p>
<p>The distinction though is based in the principle that &quot;no man is bound to accuse himself.&quot; It is a reaction against the practice of forcing people to affirm their own culpability in <a href="https://en.wikipedia.org/wiki/Star_Chamber" rel="noreferrer">Star Chamber</a> proceedings and ecclesiastical courts (<em>Constitution Annotated</em>, <a href="https://constitution.congress.gov/browse/essay/amdt5-4-1/ALDE_00000864/" rel="noreferrer">Amdt5.4.1</a>) It is an <em>exception</em> to the general common law principle that all relevant evidence can be compelled for production to the court, in furtherance of its truth-seeking function.<sup>1</sup></p>
<p>For a comparative look, Canada makes the same distinction:</p>
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<p>Both the common law and the <em>Charter</em> draw a fundamental distinction between incriminating evidence and self-incriminating evidence: the former is evidence which tends to establish the accused's guilt, while the latter is evidence which tends to establish the accused's guilt by his own admission, or based upon his own communications. The s. 7 principle against self-incrimination that is fundamental to justice requires protection against the use of compelled evidence which tends to establish the accused's guilt on the basis of the latter grounds, but not the former.</p>
<p><em>Phillips v. Nova Scotia (Commission of Inquiry into the Westray Mine Tragedy)</em>, <a href="https://canlii.ca/t/1frk2#par28" rel="noreferrer">[1995] 2 S.C.R. 97 at para. 28</a>.</p>
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<p><sup>1. This is a general common-law principle, but for language from the Canadian context: &quot;The truth-seeking function of the trial creates a starting premise that all relevant evidence is admissible.&quot; See <em>R. v. Grant</em>, <a href="https://canlii.ca/t/ggjsm#par18" rel="noreferrer">2015 SCC 9 at para. 18</a>.</sup></p>

<p>The privilege against self-incrimination in the US 5th amendment isn't a right to not testify if you don't feel like it. It doesn't say &quot;a person may not be compelled to testify&quot; it says &quot;nor shall [a person] be compelled in any criminal case to be a witness against himself&quot;. It's not that the information in your head is privileged in the way that communication with a lawyer is. Rather the 5th amendment confers the right to not be <em>forced</em> to testify against yourself.</p>
<p>The right isn't intended to protect against revealing information you don't want to reveal, but rather to protect against the government putting you in a position where you are legally compelled to give criminal evidence against yourself or else suffer some penalty for refusing to give the evidence (such as the penalties for perjury, or by having the refusal to testify itself taken as evidence of guilt).</p>
<p>As such it isn't simply &quot;this information is in my head, therefore it's privileged and I don't have to give it to the state if I don't want to&quot;. There has to be a real danger that responding to a specific request would incriminate you:</p>
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<p>To be self-incriminating, the compelled answers must pose a “substantial and ‘real,’ and not merely a “trifling or imaginary hazard” of criminal prosecution.</p>
<p>Source: <a href="https://www.law.cornell.edu/wex/fifth_amendment" rel="noreferrer">https://www.law.cornell.edu/wex/fifth_amendment</a></p>
</blockquote>
<p>A judge can overrule a claim of the privilege if it is clear that complying with the request cannot possibly self-incriminate. And if a witness has been granted immunity from prosecution for some criminal act, answering questions about that crime can no longer pose any danger of leading to criminal prosecution and thus they can no longer &quot;plead the 5th&quot; to those questions.</p>
<p>Also, while the <em>contents</em> of pre-existing documents generally cannot be protected by the right against self-incrimination (because you weren't legally compelled to write those documents), it <em>is</em> possible to refuse to hand over documents when revealing the <em>existence</em> of the documents is itself giving the government new self-incriminating evidence:</p>
<blockquote>
<p>What the privilege protects against is the compulsion of testimonial disclosures. … A person may be compelled to produce specific documents even though they contain incriminating information. If, however, the existence of specific documents is not known to the government, and the act of production informs the government about the existence, custody, or authenticity of the documents, then the privilege is implicated.</p>
<p>Source: <a href="https://constitution.findlaw.com/amendment5/annotation04.html#who" rel="noreferrer">https://constitution.findlaw.com/amendment5/annotation04.html#who</a></p>
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<p>Basically, it's not the information <em>itself</em> that is privileged, nor a distinction of what medium the information is stored in. It's the specific <strong>act</strong> of self-incrimination that is privileged, so that the government cannot compel you to do that.</p>

united-states fifth-amendment