Objectives. Discrepancies in forensic psychological opinions concerning the same case are relatively frequent. Such differences of opinion make the judiciary authorities distrustful of expert psychologists' professional competence and result in appointing new experts.
Case reports. Several relevant cases are described in the paper and the reasons of differences in forensic psychological opinions are discussed. The discrepancies resulted either from formal errors, an inappropriate choice of diagnostic methods, or from erroneous interpretation.
Commentary. These causes of discrepancies in psychological opinions could be avoided or at least minimized if standards for expert reports were developed and propagated. Such standards would serve expert psychologists as a model to be followed in their preparation of clear, coherent and comparable opinions, comprehensible and easily assessable by courts. The development of such a standard is being discussed.