Duhaime's Law Dictionary

Personal Knowledge Definition:

Something a witness actually saw or heard.

The term personal knowledge is mostly, used, in law, in the context of the requirement of the contents or averments of an affidavits. Allegations of fact in an affidavit which are not within the personal knowledge of the affiant are either hearsay, opinion or argument.

As described by Justice Moore of the Court of Appeal of Louisiana in State of Louisiana v Cecil:

"Affidavits shall be made on personal knowledge, shall set forth such facts as would be admissible in evidence, and shall show affirmatively that the affiant is competent to testify to the matters stated therein.

"Personal knowledge means something the witness actually saw or heard, as distinguished from what he learned from some other person or source."

Similarly, in Stevens v. Water District One of Johnson County, Justice Judy Robinson of the United States District Court (Kansas) wrote:

"[U]nder the personal knowledge standard, an affidavit is inadmissible if the witness could not have actually perceived or observed that which he testifies to. Statements of mere belief in an affidavit must be disregarded....

"To enforce this rule, the court ordinarily does not strike affidavits, but simply disregards those portions that are not shown to be based upon personal knowledge "


  • State of Louisiana Department of Transportation and Development v Cecil, 966 So. 2d 131 (2007)
  • Stevens v. Water District One of Johnson County, 561 F. Supp. 2d 1224 (2008)

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