An affiant is the person who signs an affidavit — a written statement sworn to be true before a notary or other authorized official. Once you sign as the affiant, every fact in the document carries the same legal weight as testimony given in a courtroom, and lying can be prosecuted as perjury with a maximum federal sentence of five years in prison.1Office of the Law Revision Counsel. 18 USC Ch. 79 Perjury The role is simple to describe and serious to accept.
Who Qualifies as an Affiant
Not anyone can serve in this role. Federal court rules require that an affidavit be “made on personal knowledge, set out facts that would be admissible in evidence, and show that the affiant or declarant is competent to testify on the matters stated.”2Legal Information Institute. Federal Rules of Civil Procedure Rule 56 – Summary Judgment Three requirements come out of that standard.
Personal Knowledge
You have to know the facts firsthand. If you watched a car accident happen, you can describe what you saw. If your neighbor told you about it later, you can’t put that in an affidavit as if you had been there — that’s hearsay, and a court will strike those portions. One narrow exception exists for search-warrant affidavits, where law enforcement officers routinely include information from witnesses, informants, and other investigators because the strict rules of evidence don’t apply at the warrant stage.3Federal Law Enforcement Training Centers. Affidavit Writing Made Easy
Legal Capacity
You need to be old enough and mentally competent to understand what an oath means. In practice, that means being at least 18 and able to grasp that false statements carry legal consequences. A court won’t accept an affidavit from someone who lacks the capacity to appreciate the significance of swearing.
Oath or Affirmation
Before the document has any legal force, you have to swear or affirm that its contents are true. Federal Rule of Evidence 603 requires this of anyone providing testimony, and it applies equally to written sworn statements.4Legal Information Institute. Federal Rules of Evidence Rule 603 – Oath or Affirmation to Testify Truthfully An affirmation is available for people with religious or personal objections to swearing an oath. The legal effect is identical.
Affiant vs. Deponent
These two terms get mixed up because both involve sworn testimony given outside a courtroom. The difference is the format. An affiant provides written testimony in an affidavit, prepared in advance and signed before a notary. A deponent gives oral testimony during a deposition, answering live questions from attorneys with a court reporter recording the exchange. Both are under oath and both face perjury exposure for lying. Only the setting changes.
What Signing Actually Involves
An affidavit without proper notarization is generally worthless as evidence. The notary public does two things: verifies your identity using a government-issued ID and witnesses the oath. The notary confirms you understand what you’re signing and are doing so voluntarily, administers the oath, and applies an official seal. Skip any of those steps and the opposing party has grounds to argue the affidavit is inadmissible.
Certain affidavits carry extra formatting requirements. Real estate affidavits often need specific statutory language to be recorded with a county clerk. Affidavits filed in federal court must meet the standards set by the Federal Rules of Civil Procedure, including the personal-knowledge requirement.2Legal Information Institute. Federal Rules of Civil Procedure Rule 56 – Summary Judgment
Remote Online Notarization
Forty-seven states and the District of Columbia now authorize remote online notarization, which lets you appear before a notary by video call rather than in person.5National Association of Secretaries of State. About Remote Electronic Notarization Virginia launched the first remote notarization law in 2011, and adoption accelerated during the pandemic. Identity verification and the oath still happen — the notary typically uses knowledge-based authentication questions and credential analysis to confirm who you are. Requirements vary by state, so check that the process complies with the rules in your jurisdiction before relying on it.
The Unsworn Declaration Alternative
Federal law offers a shortcut many people don’t know about. Under 28 U.S.C. § 1746, you can substitute an unsworn declaration for a traditional notarized affidavit in most federal proceedings. Instead of finding a notary, you sign a statement that includes the language: “I declare under penalty of perjury that the foregoing is true and correct,” along with the date and your signature.6Office of the Law Revision Counsel. 28 USC 1746 Unsworn Declarations Under Penalty of Perjury
The legal effect is the same as a sworn affidavit, including exposure to perjury charges if you lie. The practical advantage is convenience: no notary appointment, no fee, no waiting. Many federal courts and agencies accept declarations interchangeably with affidavits. State courts are a different matter. Some accept them, others require the traditional notarized form, so check the local rules before skipping the notary.
What Happens if You Lie
Signing a false affidavit is a crime, not a paperwork mistake. Three layers of consequence can hit at once.
Criminal Perjury
Under federal law, anyone who knowingly states something false in a sworn document — or in an unsworn declaration under penalty of perjury — commits perjury, with a maximum sentence of five years in federal prison.1Office of the Law Revision Counsel. 18 USC Ch. 79 Perjury A separate federal statute covers false declarations made in court proceedings and carries the same five-year maximum.7Office of the Law Revision Counsel. 18 USC 1623 False Declarations Before Court or Grand Jury State perjury laws vary but most treat the offense as a felony with prison time ranging from one to five years. The false statement must be material. An honest mistake or trivial error generally won’t trigger prosecution, but a deliberate lie about a fact that could change the outcome of a case will.
Court Sanctions
Even without a criminal case, an affiant who submits a bad-faith affidavit in federal court faces immediate consequences. Under Rule 56(h), a judge can order the offending party to pay the other side’s attorney’s fees, hold the affiant or their attorney in contempt, or impose other sanctions.2Legal Information Institute. Federal Rules of Civil Procedure Rule 56 – Summary Judgment Sanctions apply when the court is satisfied the affidavit was submitted in bad faith or solely to delay the proceedings.
Civil Liability
A false affidavit can also expose the affiant to a civil lawsuit. If the false statements cause harm — someone loses custody of their children or gets wrongfully arrested based on fabricated facts — the injured party may have grounds to sue for damages. Officers who include false information in warrant affidavits face civil rights lawsuits for constitutional violations. Outside the law enforcement context, injured parties may pursue claims based on fraud or other theories depending on the jurisdiction. Criminal exposure, court sanctions, and civil liability stacked together make the risk of lying far greater than most people assume.
How the Other Side Can Challenge Your Affidavit
Signing doesn’t settle the matter. An affidavit isn’t bulletproof just because it’s sworn, and the opposing party has several tools to attack it.
The most direct is an objection under Rule 56(c)(2), which allows a party to argue that material in an affidavit can’t be presented in admissible form. If you included hearsay, speculation, or statements outside your personal knowledge, those portions can be excluded. A judge won’t necessarily throw out the whole document, but the offending paragraphs lose their evidentiary weight.
Courts also apply what’s known as the sham affidavit doctrine. If you give testimony in a deposition and then submit an affidavit that flatly contradicts what you said earlier, the court can disregard the affidavit. You don’t get to create a factual dispute by arguing with yourself. The doctrine is narrow — it only applies when the contradiction is clear and you offer no reasonable explanation for the change. Affidavits that merely clarify ambiguous earlier statements survive this challenge.
Procedural defects give the other side another opening. If the notarization was improper, the affiant lacked personal knowledge, or the affidavit doesn’t comply with local court rules, the opposing party can move to have it excluded. An affidavit struck from the record at a critical moment can sink the case it was meant to support, so the care you take at the signing stage matters later.