State v. Mann

New Mexico (plaintiff) charged William Mark Mann (defendant) with intentional child abuse resulting in death after the victim was impaled with a screwdriver. At trial, Mann's medical expert testified the impalement could have been accidental. One juror, an engineer, privately used engineering calculations to check the expert's testimony, estimated the odds of accidental impalement at less than 1 in 20 million, and shared that estimate with the rest of the jury; other jurors also shared their own experiences with children and with medical experts generally during deliberations. Mann was convicted and appealed, arguing the engineer-juror had improperly introduced new, uncross-examined evidence that tainted the verdict.