Veterinary professional practice can be performed in many forms, including expert activity. The importance of veterinary expertise is, however, often underrated and limited to only one of its areas. Nonetheless, veterinary expert opinions have significant social, legal, and economic impacts. This study investigates veterinary expertise from an interdisciplinary, comparative perspective. Ethical and legal analysis and interpretation are performed. Essential concepts and relevant aspects of veterinary expertise are analysed. Legally relevant factors of an expert opinion are identified. The relationship between the law, the language, and the understanding of the role and duties of a veterinary proficient is demonstrated. A variety of possible expert opinions and the multiplicity of veterinary scopes of such activity is presented. It is argued that the ranges of forensic veterinary medicine and of veterinary expertise are broader than is predominantly assumed. Veterinary forensic medicine is a crucial part of veterinary specialisation. Ethical and legal basics, and the scope of veterinary expert’s liability, are revealed and discussed. The conclusion is that the duties and responsibilities of expert veterinarians are particularly great due to the exercise of the public trust profession, with large importance for the whole society. Their observance is, however, crucial to ensure the highest quality of expert opinions issued by veterinarians.