ORDINARY EXPERIENCE

The difference between expert and lay witnesses is that the former have a unique expertise that most people do not, from accounting to engineering or medical knowledge to a nearly limitless array of fields, and may speak fairly freely on their topic if useful in the trial.  Fact witnesses, on the other hand, may only testify to what they saw or heard, informed by ordinary every-day experiences.

Maybe it says something about the state of the country at the time of Prohibition that a 1929 court did not require an expert witness to identify corn whiskey with reasonable certainty.  Lay witnesses would know its taste and smell well enough from ordinary experience.