Straipsnyje baudžiamuoju teisiniu, filosofiniu, medicininiu bei teologiniu aspektais analizuojami žmogaus gyvybės pradžios ir pabaigos momentai. Atskleidžiant nevienareikšmiškai traktuojamas bei vertinamas šių reiškinių sampratas straipsnyje formuluojami aspektai, lemiantys žmogaus gyvybės pradžios ir pabaigos momentų traktavimą baudžiamo joje teisėje bei šių sampratų vienodo suvokimo būtinumo reikšmę nusikalstamų veikų kvalifikavimui kaip nužudymų. Both in criminal law science and in the judicial practice there are a lot of discussions as to what should be considered as the beginning and end of human life. Birth and death are not instantaneous acts, but rather processes made up of time-spans that can be construed as evidence of the beginning or end of a human life. From a biological point of view the human life is a constant, continuous metabolic process after cessation of which the human life also ceases. These circumstances very much aggravate the definition of criteria of the moments of beginning and end of human life. There are disagreements in the criminal law science with respect to from which moment the human life is to be protected by the criminal law. Herewith this presupposes also the other problematic question—what is to be considered a “living human” as a homicide subject (a victim). Complication of the said question is also determined by the fact that it is related not only to legal but also to medical, religious, and moral aspects. This article exactly analyses certain aspects of the beginning and end of human life in the context of the homicide composition attributes. Three main theories of the beginning of human live that is protected according to the standards of the Criminal Code are yet distinguished in the juridical literature, i.e. a person is a human being from: a) the moment of conception; b) a certain moment of the foetal development; c) the moment of birth. It is suggested in the article to follow the following criteria of establishing the initial moment of human life: the initial moment of human life should be considered as complete separation of the foetus from the mother, regardless whether or not the umbilical cord has been cut or the placenta detached, and when breathing or other evidence of life such as beating of the heart, pulsation of the umbilical cord, or voluntary muscle movement are noticed. It’s the authors’ considered opinion that such attitude towards this problem mostly satisfies the level of achievements of modern medicine. Judicial practice and the theory of criminal law is interested not only in the question since when human life should be considered as conceived but also until what moment the life continues, for dead human just like unborn one cannot be a subject of homicide (a victim). Establishment of the moment of the end of human life is not as problematic as the moment of the beginning of life. In the authors’ opinion, it is most adequate to consider the moment of human death as the complete and irreversible cessation of function of the entire brain, including the brain stem, when irreversibility of this cessation is determined and diagnosed in accordance with the acceptable legal instruments. It should be emphasized that only irreversible death of the entire brain is the basis for diagnosing human death. Irreversibility of brain death is diagnosed on the grounds of a number of clinical conditions defined by medical science.