Personal knowledge means knowledge of a circumstance or fact gained through firsthand observation or experience. Generally, statements in affidavits are presumed to have been made on personal knowledge, unless it appears affirmatively, or by fair inference, that they could not have been, and were not on such knowledge. It is also called as firsthand knowledge.
In Valenzuela v. State & County Mut. Fire Ins. Co., 317 S.W.3d 550 (Tex. App. 2010), the court observed that “An affidavit not based on personal knowledge is legally insufficient.”
Further, in Shah v. Getz, 1994 Ohio App. LEXIS 2780 (Ohio Ct. App. 1994), the court observed that “Personal knowledge is knowledge of factual truth that does not depend on outside information or hearsay. An affidavit without an averment of personal knowledge must show personal knowledge specifically.”