A court or arbitrator can infer from a failure to produce evidence known to have existed, or a refusal to answer questions about it, that the missing evidence or testimony hurts that party’s claim or defence. Typically this is because the party in question has refused to produce the evidence, destroyed the evidence, presented unlikely excuses for what happened to the evidence or invoked a privilege to avoid presenting the evidence. An adverse inference will typically apply the worst reasonable interpretation of what the missing evidence might show for the party that caused it to be absent. Adverse inference are becoming more common as digital data that demonstrably existed vanishes in the course of proceedings. The risk of an adverse inference being drawn is a crucial reason for rapidly implementing litigation holds.
In English law the best known recent example of an adverse inference being drawn is in the so called Wagatha Christie defamation case, Vardy v Rooney, in which the wife of one prominent footballer, Rebecca Hardy sued another, Coleen Rooney, for defamation based on Rooney’s own published investigative conclusion that Vardy had leaked confidential stories to the British tabloid press (Wagatha Christie being a portmanteau of the Wives and Girlfriends acronym used by the press for footballer’s romantic partners and the name of the detective novel writer Agatha Cristie.) The central question was whether Vardy had in fact leaked, and this turned on messages sent to and from Vardy’s publicist, which had either been deleted from all of Vardy’s devices, or lost when the publicist’s cell-phone had somehow been mysteriously dropped into the North Sea. The court, applying an ancient British case Armorie v Delamirie (1721) concluded the explanations of a series of unlikely events that led to the loss of the messages was not credible and that the assumption must be that the messages Vardy and her publicist were accused of sending must both exist and be damning.