Legal Definitions - falsus in uno doctrine

The falsus in uno doctrine is a legal principle that allows a jury to question the overall credibility of a witness. If a jury believes that a witness has intentionally lied about a significant or important fact (a "material issue") during their testimony, the jury has the discretion to disregard all of that witness's testimony, not just the part that was false. This doctrine reflects the idea that if someone is willing to lie about one important thing, they might be lying about other things as well.

• Criminal Trial - Alibi Witness:

  During a robbery trial, a witness testifies under oath that the defendant was with them at a specific restaurant across town at the exact time the robbery occurred, providing a detailed account of their evening. However, the prosecution later presents irrefutable security camera footage showing the witness alone at a different location, nowhere near the restaurant, at that precise time. If the jury concludes that the witness intentionally fabricated their alibi testimony regarding their whereabouts, they may choose to disbelieve not only the alibi itself but also any other statements the witness made, such as their claims about the defendant's character or previous interactions.

• Civil Case - Personal Injury Claim:

  In a lawsuit seeking damages for injuries sustained in a car accident, the plaintiff testifies that their back injury is so severe they can no longer perform basic household chores or lift anything heavier than a small book. The defense then introduces surveillance video showing the plaintiff actively participating in a strenuous gardening project, lifting heavy bags of soil, and bending repeatedly without apparent difficulty. If the jury determines that the plaintiff intentionally exaggerated or lied about the extent of their physical limitations to increase their compensation, they could apply the falsus in uno doctrine and disregard the plaintiff's entire testimony, including their account of how the accident happened or their claims of pain and suffering.

• Contract Dispute - Key Meeting Details:

  Two companies are in a legal dispute over the terms of a verbal agreement. A key witness for one company testifies about a crucial meeting where specific delivery dates and payment schedules were allegedly finalized. The witness states unequivocally that the meeting took place on a Tuesday and that certain conditions were agreed upon. However, emails and calendar entries from both parties later confirm that the meeting actually occurred on a Friday, and the witness's own prior written notes contradict their testimony about the agreed-upon conditions. If the jury finds that the witness intentionally misrepresented these material facts about the meeting's date and outcomes, they might decide to discredit all of that witness's testimony regarding the contract terms, even aspects that were not directly contradicted by other evidence.