According to the different relationship between evidence and the object of proof, evidence can be divided into two categories, that is, the substantial evidence and the auxiliary evidence. While the substantial evidence is thought to be “produced” by the existence or occurrence of the facts to be proved, the auxiliary evidence is regarded relatively independent of the facts to be proved. Auxiliary evidence can be further broken into various sub-categories, among which the distinction between in-case evidence and out-case evidence is the most important type decided by the “distance” between the facts to be proved and the facts bringing forth the auxiliary evidence. There are many problems in distinguishing the substantial evidence from the auxiliary evidence correctly, such as the imprecise definition of the object of proof, and the in-case auxiliary evidence being misapprehended as the substantial evidence.To some extent, the prescriptive implication of this classification lies in the establishment of some practical permission and prohibition for the abstract proof standards, which can not only overcome the difficulties in judgment but also prevent the judicial arbitrariness. In western criminal procedures, due to the different proof standards for various processes such as conviction, arrest, stop and search, the applicable rules are different accordingly and generally reasonable. However, these rules and methods can not be directly found in the statutes but more as a legal and practical conception. Comparatively, in the corresponding and similar proving processes in Chinese criminal procedure, the auxiliary evidence, especially the out-case one is often not properly regulated due to its illegal status, while the substantial evidence and the in-case auxiliary evidence, especially the former are unduly relied on.The classification and its prescriptive implication of substantial and auxiliary evidence are universal and fundamental for law and practices. Thus, while research and education in this aspect should be strengthened, steps should also be taken in legislation and judicial interpretation. |