A rare case of a lethal outcome due to iatrogenic damage to the intercostal vessel, a collateral branch of the posterior intercostal artery, is described. The little-known features of the topography of this vessel (location on the upper edge of the underlying rib), which requires further study in the context of variable anatomy, are given. The risks associated with deviations from the traditionally recommended sites of pleural puncture (below the eighth intercostal space to the scapular line) are substantiated. An analysis of the characteristics of bleeding arising from the intercostal vessels (from two ends, under high pressure, etc.) is given, which implies the extreme importance of a timely diagnosis. Differing points of view on the legal assessment of malpractice when care is delivered by a series of doctors, and the legal necessity of determining the «point of no return» (the latest moment after the onset of bleeding, in which medical aid can still prevent an unfavorable outcome), are considered. An opinion is expressed on the need for the active participation (initiative) of an expert in the provision of expertise.