The issues of identifying cause-and-effect relation (CAER) between professional violations of medical workers and the following harm to health or fatality of a patient are quite complex, insufficiently studied and covered in available domestic scientific and medical publications. This article deals with the issues of identifying and determining CAER between defects in medical treatment (MT) and fatality. The object of the study were the 177 opinions of forensic panel examination (FPE) on the archival material of the forensic medical examination department of the «National Bureau of Expertises» of the National Academy of Sciences of the Republic of Armenia for the period from 2013 to 2018.

In order to analyze the structure of defects of MT, we classified them as follows: diagnostics defects; defects of treatment; defects in organization of medical treatment; defects in medical record-keeping.

According to the opinions of the 177 FPE, in 132 (74.6%) cases, various defects while MT were detected, and in 45 (25.4%), they were not registered. According to the 132 opinions of the FPE, 250 defects while MT were recorded. Diagnostics defects (34.8%) and treatment defects (31.2%) were most common, and defects in the organization of MT (12.0%) were less common.

In the presence of defects while MT in 30.3% of cases, CAER was revealed between the frequency of defects while MT and the probability of fatality. The probability of fatality was most affected by defects in diagnosis and treatment. Thus, the relative risk was 2.41 at 95% CI (confidence interval) from 1.31% to 4.44% and 15.65 at 95% CI from 5.01% to 48.87%, accordingly.