The Two Witness Rule
An investigative guideline that has been used in some courts, by Woodward and Bernstein, and even in the Bible
One challenge for prosecutors or reporters is knowing when you have enough evidence to charge or write. There is no absolute rule, but some version of the “two witness rule” has been used at times by federal courts, Woodward and Bernstein, and even the Bible, so it’s a good start and worth knowing!
The basic concept of the “two witness rule” is that a person cannot be convicted solely on the word of a single witness. If all you have is one person’s word against another’s, that generally is not good enough.
This rule (or guideline) has a very long history – it actually appears in the Hebrew Bible, which Christians refer to as the Old Testament. In Deuteronomy, Moses sets out the rule for the Israelites in two slightly different formulations:
“On the evidence of two or three witnesses the death sentence shall be executed; a person must not be put to death on the evidence of only one witness.” Deuteronomy 17:6.
“A singe witness shall not suffice to convict a person of any crime or wrongdoing in connection with any offense that may be committed. Only on the evidence of two or three witnesses shall a charge be sustained.” Deuteronomy 19:15.
In modern times, this idea has declined in importance.
In the United States, the “rule” does not actually hold as a matter of law in most types of criminal cases – one witness theoretically can be enough to support an arrest or a conviction, even when the witness is an accomplice who might have great incentive to lie. As one court put it, “even the testimony of a single accomplice witness is sufficient to sustain a conviction, provided it is not ‘incredible on its face,’ or does not ‘def[y] physical realities.”
But the “rule” does still hold explicitly for one type of criminal case – perjury cases under Title 18, United States Code, Section 1621 for false testimony in a federal case.
In a 1945 case, the United States Supreme Court noted that the “two witness rule” for perjury cases was “deeply rooted in past centuries” and that its application in federal and state courts was “well nigh universal.” In perjury cases, the rule requires (1) the direct testimony of a second witness and/or (2) other evidence that is independent of the first witness and corroborates the first witness. (Lawyers should note that the rule generally does not apply to prosecutions for other types of false statements, such as prosecutions under Title 18, United States Code, Section 1001).
While the “two witness rule” now is very limited as a matter of law, it still holds great practical value.
Reporters usually want at least two sources for key assertions, especially controversial points that could be disputed. (I did back when I was a newspaper reporter)
Bob Woodward and Carl Bernstein refer to this in their classic book, All The President’s Men. As the reporters investigated Watergate, they had difficulty getting their sources to confirm what had happened and thus had to be careful about what went into print. “Gradually, an unwritten rule was evolving: unless two sources confirmed a charge involving activity likely to be considered criminal, the specific allegation was not used in the paper.”
And prosecutors probably would have difficulty proving their case beyond a reasonable doubt if relying on a single witness. This affected my practice as a lawyer in two ways.
First, I generally look for ways to corroborate a witness whenever possible. When I was a prosecutor and met with a witness in a white-collar criminal case, I often would check the data or documents immediately afterwards to see if I could corroborate at least part of what the witness said. And as a defense lawyer, I’ve sometimes found that prosecutors took their witnesses at face value without checking independent evidence that should have raised significant doubts about whether their witnesses were reliable.
Second, when I was a prosecutor, I was trained to always have someone with me when I interviewed a witness. This way, if we ever needed to prove what a witness said or did not say, I would have someone there to back me up. Having a “prover” makes it easier to prove what happened and prevents situations from devolving into one person’s word against another’s (it also reduced the potential for situations where I might become a witness myself).
By the way, this is something that lots of TV shows and movies get wrong about real-life investigations; FBI agents typically work in pairs in part so that there will be two witnesses, not one, if something significant happens or is said.
The “two witness rule” now is very limited as a “rule,” but it’s still a useful guide as you read news articles and consider criminal cases.
Be skeptical if you read a news article that relies only on one source, especially if the source is anonymous or did not personally observe the events that the source describes.
Be very skeptical if you see a criminal case that centers on an event that only the defendant and one other person were present for.
The number of witnesses does not matter anymore as a strict rule of law, but an article or case resting on a single source should have very good corroboration.
Sources: The Deuteronomy quotes come from the New Oxford Annotated Bible (third edition). The quote from All The President’s Men by Carl Bernstein and Bob Woodward is from chapter 4. The Supreme Court case that I cited is Weiler v. United States, 323 U.S. 606 (1945). One Second Circuit case discussing whether a single witness can be sufficient to sustain a conviction is United States v. Truman, 688 F.3d 129 (2d Cir. 2012) (“We have explained that even the testimony of a single accomplice witness is sufficient to sustain a conviction, provided it is not ‘incredible on its face,” or does not ‘def[y] physical realities.’”). An archived Department of Justice summary of the “two witness” rule is available here.
About the Author: I was a federal prosecutor in Chicago from 2008 to 2019 and have been in private practice since 2019, now as a solo practitioner focusing on health care fraud, white-collar criminal cases, and data analytics. Before becoming a lawyer, I was a reporter for the Chicago Tribune and also worked for other news organizations, including the Associated Press and the Dallas Morning News. I had been thinking about writing something about the “two witness rule” for years and decided to write this after hearing it mentioned in an ethics discussion at the American Bar Association’s 2023 white collar crime conference.