Johnson v. State

A factfinder at a trial applies common sense drawn from shared human experience to the evidence to reach a fair determination of the facts. Some evidence, however, is beyond the common experience of most people. Expert testimony may be necessary for the factfinder to decide the significance of such evidence.

Expert testimony is often required to explain scientific or technical matters. But expert testimony is not required simply because one can explain a matter scientifically. For example, a jury can be expected to readily understand the significance of testimony that a clock or a thermometer…