Medical Expert Testimony *

That sort of capacity which involves not the organic powers, moral and mental, requisite for all testimony, nor yet the emotional power of unbiased observation and statement, but the skill to acquire accurate conceptions which may be termed experiential capacity. The person possessing it is commonly called an expert. This capacity may be obtained by special training or experience, or by both. It is, in every case, a relative one. That is, relative to the subject about which the expert is to testify. He may be sufficiently skilled in one subject and totally unskilled in another. He may, for example, be competent to testify that the deceased was asphyxiated, but not competent to say whether or not it was coal-gas or water-gas which caused death. He may be competent to say that the instrument causing death was sharp, but incompetent to say that the stains on the instrument were human blood. The methods for obtaining this capacity may be by particularly prearranged training prior to entrance into his special field, or by occupational work which followed some form of previous training. Many famous experts have had very ordinary training prior to gaining experience in this work by occupation. Sometimes one of these methods shades into the other. Either is acceptable.