Can a witness refuse to answer a question in a civil proceeding if it would incriminate her on a unrelated criminal matter?
<p>Basically the title. I saw on a lawyer drama that a witness was compelled to answer because it was not a criminal case. But if the truthful answer uncovers a criminal matter that would incriminate the witness, can she refuse to answer on grounds of Fifth Amendment, even if it is civil case?</p>

<p>In <a href="https://supreme.justia.com/cases/federal/us/266/34/" rel="noreferrer">McCarthy v. Arndstein</a>, 266 U.S. 34, the Supreme Court declared that</p>
<blockquote>
<p>The privilege is not ordinarily dependent upon the nature of the
proceeding in which the testimony is sought or is to be used. It
applies alike to civil and criminal proceedings, wherever the answer
might tend to subject to criminal responsibility him who gives it.</p>
</blockquote>
<p><a href="https://supreme.justia.com/cases/federal/us/406/441/" rel="noreferrer">Kastigar v. United States</a>, 406 U.S. 441
It can be asserted in any proceeding, civil or criminal, administrative or judicial, investigatory or adjudicatory, [Footnote 10] and it</p>
<p>Page 406 U. S. 445 likewise finds that the privilege</p>
<blockquote>
<p>can be asserted in any proceeding, civil or criminal, administrative
or judicial, investigatory or adjudicatory, and it
protects against any disclosures that the witness reasonably believes
could be used in a criminal prosecution or could lead to other
evidence that might be so used.</p>
</blockquote>
<p>There may be some confusion over criminal vs. civil cases, so first we should restate the self-incrimination clause:</p>
<blockquote>
<p>nor shall be compelled in any criminal case to be a witness against
himself</p>
</blockquote>
<p>There are many ways that this language can be interpreted, for example it could mean that a person who is a criminal defendant cannot be compelled to testify against themselves in that case; or that the protection applies to a <em>possible, future</em> criminal case against them (when they are the defendant in a criminal trial); or when they are a non-defendant witness in some criminal trial. Instead, the courts interpret the privilege as protection against <em>any</em> being compelled to testify, when that testimony has a tendency to incriminate.</p>
<p>The line that exists, w.r.t. civil cases, is that you can be compelled to testify against your civil case interest – you can be compelled to testify that you breached a contract, for example. When testifying in a criminal case, you can be compelled to testify to a breach of contract. It is not about the nature of the case where you are testifying, it is about the nature of the <em>possible</em> case where that testimony could be used against you.</p>

united-states fifth-amendment self-incrimination