Black's law Dictionary defines adverse inference as "a detrimental conclusion drawn by the fact-finder from a party's failure to produce evidence that is within the party's control."
Here, Norman J. Van Valkenburgh caused the controversy with his erroneous survey, so his testimony was central to the case. He attended the trial daily and assisted the Preserve, so he was clearly under their control. But his testimony would have been subject to cross examination against prior sworn testimony from the 2001 trial, which was at odds with Mohonk's current theory in this case. The judge was in possession of this unfavorable testimony, so it was not mere speculation. Furthermore, Mohonk was informed that if they failed to call their own surveyor to defend his survey, that the defendants would seek a negative inference.