© D.L. Crumbley
Three Approaches to Testifying
Express opinion based upon facts personally observed, or facts communicated to him by another expert.
Be present in courtroom and express opinion on such evidence (that is not in dispute).
Base an opinion on a hypothetical question embracing evidence in the record.
Source: J.R. Waltz, Evidence, New York: Foundation Press, 1999, p. 15.