Due to the difficulty of proving the composition of crimes related to occupying the highest position in the criminal hierarchy, a study was conducted aimed at searching for morphogenetic features of criminals in this category. Research material: fingerprint cards of 46 «thieves in law». Comparative material: fingerprint cards of 97 serial killers and 1.032 law-abiding citizens. The types of papillary patterns were recognized in the fingerprints. Based on the frequency analysis, numerous intergroup differences of dermatoglyphic signs were revealed (statistically significant at the level of p<0.05). The «thieves in law» are characterized by the presence of a transitional type of pattern, the relatively frequent occurrence of arc and curl types of patterns, left-sided asymmetry of pattern types on the fingers of the radial group, right-sided asymmetry on the fingers of the ulnar group, the minimum severity of the radial-ulnar gradient on the fingers of the right hand and its maximum severity on the fingers of the left hand. In total, 17 diagnostically significant signs were found for the differential diagnosis of «thieves in law» with law-abiding citizens and 11 more signs with serial killers. An integral assessment of the informativeness of a complex of diagnostically significant dermatoglyphic signs showed that on their basis, in 1/3 of cases, a probabilistic (p≈0.90) judgment about the group affiliation of the examined person is possible. The diagnostic results should be considered as the basis for a more complete and comprehensive (criminological, social, psychological, medical and biological) study of the identity of the person being checked (the criminal).