A non-expert witness, i.e., a lay witness, typically is limited to testimony based upon personal observation and knowledge. However, a lay witness may properly testify and/or state an opinion if the opinion includes facts showing that the opinion is rational, based on the witness’s perception, relevant, and helpful in understanding other facts in the document or matter. (Evidence Code § 800.) To establish this foundation, the testimony, statement, or declaration must all show:

  • Sufficient reasons and explanations for the opinion;
  • The factors considered; and
  • The reasoning employed.

The facts about which the witness testifies must be of such a nature that the witness cannot adequately describe those facts without using inferential words. In addition, notwithstanding the above restriction, lay opinion testimony is admissible if it has been held admissible by case law or statute. Some examples of subjects considered appropriate for opinion testimony by lay witnesses include:

  • Age.
  • Distance.
  • Future earning capacity.
  • Handwriting identification. (Evidence Code § 1416.)
  • Health, injury, or emotional distress testimony by subject.
  • Health, injury, or emotional distress testimony by another.
  • Identity and appearance, based on witness’s own perception.
  • Intoxication – from alcohol or drugs.
  • Ownership, when not in issue.
  • Parentage.
  • Possession.
  • Sanity. (Evidence Code § 870; must have intimate knowledge of the individual being adjudged or of a writer at the time of the writing.)
  • Seatbelts. Whether expert testimony is required on the effect of not having worn seatbelts is decided on a case-by-case basis.
  • Size.
  • Speed.
  • Value of one’s own property. (Evidence Code §§ 810, 813-815.)
  • Value of one’s own services.
  • Value of ordinary services “of a nontechnical nature.”