As during the trial the appellant didn't argue the relevance of the excluded evidence to comparative negligence factors (including risk avoidance), and the jury wasn't instructed on these factors, no material harm from the exclusion of employee handbook, given that the verdict found negligence, but less than a preponderance, barring any recovery under comparative negligence.
Similarly, appellant didn't argue below that the excluded expert testimony would be useful in allocating fault, so no material hamr from exclusion.
Dissent:
As comparative negligence is simply the degree of negligence, arguing negligence below suffices to consider the harm. Per precedent, court should have a fair assurance of the error not being dispositive.