The authors describe the peculiarities of the commissionary expertise with respect to medical practice and the difficulties facing this procedure using as an example a case of the lethal outcome caused by the injury to the right atrium as a result of unrecognized iatrogenic cardiac tamponade with the pareneteral nutrition fluid administered through the catheterized subclavian vein. It was shown that the great variety and complexity of the problems arising in such expertises should draw enhanced attention not only of forensic medical experts but also medical law specialists and other legal practitioners. It is argued that the majority of the cases of the inadequate medical care provided to the patients as exemplified by the case of death of the 43 year-old patient B resulting from the application of the unsafe technique of catheterization of the main blood vessels are usually due to the subjective («human») factors. They may occur in any health care facility regardless of its location, staff composition and competence.