An adverse inference instruction tells the jury they may — or in some jurisdictions and circumstances, must — presume that evidence a party failed to preserve or produce would have been harmful to that party's case. It is one of the most consequential remedies available for spoliation short of terminating sanctions like dismissal, because it directly shapes how the jury weighs the evidence that does exist.

Courts typically require some showing of culpability before granting an adverse inference, and the required culpability level varies: some jurisdictions permit the instruction for ordinary negligence in losing evidence, while others, particularly for electronically stored information, reserve the harshest form of the instruction for a showing of intent to deprive the opposing party of the evidence's use. The exact wording of the instruction — permissive versus mandatory — can itself be heavily litigated, since a mandatory presumption is far more damaging than a permissive one the jury is free to reject.

In a simulated Juricratic matter, an adverse inference is modeled as a strategic consequence attached to a specific spoliation event in the case's reasoning layer, letting a war-gamed run show how the instruction's presence — and whether it is framed as permissive or mandatory — shifts a claim's expected value, rather than treating it as an unexplained boost to one party's position.

Litigators move for an adverse inference instruction when opposing evidence has been lost or destroyed, building the factual record on the other party's preservation failures needed to support it, and defend against such motions by documenting good-faith preservation efforts. Because the instruction can be case-defining, both sides often treat the underlying spoliation motion as a major inflection point well before the jury ever hears the case.