To “plead the 5th” means that you exercise your rights under the 5th Amendment to the United States Constitution. The 5th Amendment provides a broad range of protections to anyone facing criminal prosecution, including the right not to be compelled “to be a witness against himself.”
It’s important to understand that this constitutional safeguard applies only to statements that are compelled. Assertions voluntarily made are not protected and can be used against you. The right, however, is not automatic—a person must affirmatively state that they are “pleading the 5th.”
The Supreme Court has held that the right not to be forced to make incriminating statements applies whether the party is innocent or guilty and whether the statement is true or false. The person making the statement has the sole discretion to determine whether the statement is potentially self-incriminating, and no other party, including prosecutors, judges, or lawyers, can force the person to testify.
A defendant in a criminal trial may exercise their right against self-incrimination under the 5th Amendment. If the defendant exercises that right, they do not take the stand at all. A witness in a criminal trial has a similar right against self-incrimination; however, a witness can be compelled to take the stand. Once there, though, a witness has absolute discretion as to which questions they refuse to answer on 5th Amendment grounds.
A party to a civil matter—a personal injury lawsuit or breach of contract action, for example—may also refuse to answer questions by claiming the privilege under the 5th Amendment. In a civil trial, the jury may view the refusal to answer questions as evidence of liability, whereas the jury in a criminal trial will customarily be instructed that they may not consider the exercise of 5th Amendment rights as evidence of guilt.
Courts have consistently found that the protections of the 5th Amendment apply only to “testimonial” evidence, limited to express or implied statements of fact or belief. For that reason, DNA tests, blood alcohol tests, and fingerprinting have generally been excluded from 5th Amendment protection. (An individual may have other legal grounds for refusing a request for DNA, blood, or fingerprints.)
Though the Supreme Court has held that pleading the 5th must not be considered evidence of guilt in a criminal proceeding, there’s still a likelihood that jurors will do that, even if the judge instructs them not to. Furthermore, as a defendant in a criminal trial, if you choose to exercise your rights under the 5th Amendment, you may not testify at all during the trial. While that might reduce the risk that incriminating evidence will come to light, it will also preclude you from presenting any testimony that could exonerate you.
The protections available to defendants and witnesses under the 5th Amendment to the United States Constitution are complex and potentially problematic. Always consult with an experienced criminal defense attorney before you exercise your rights.