A medical expert's testimony reliability assessment is accomplished within different gnoseological models. Medical practice can accentuate the intuitive synthetic orientation of an expert's reflexion.
The insufficiency of analytical component can reduce the reliability of an expert's testimony. The expert conclusions based on the concept of possibility should be replaced by the inferences containing the quantitative characteristics of probability of the analyzed matter.
The introduction of quantitative methods to the expert analysis allows to overcome the negative tendencies related to the reliability of the probabilistic conclusions in a medical expert's testimony.