The evidence that the parties claim can be provided by legal sources mainly includes purchase and sale contracts, payment vouchers, warehouse-out orders and warehouse-in orders, witness testimony, etc. Due to non-standard operations of some enterprises, complete evidence on the origin of products cannot be provided in litigation, which brings certain difficulties to the trial of the case. For example, a real estate company that built several residential buildings was accused of infringement by the flues it used. The real estate company provided a contract for the purchase of flues to prove that the flues in the residential building were not manufactured by itself, but the number of flues shown in the contract was only more than 100 meters. The court of first instance held that the authenticity of the contract provided by the real estate company could be confirmed, but its quantity was too different from the project needs, and it did not adopt its legal source defense. Based on the same evidence, the court of second instance held that the real estate company’s defense claim was established and rejected the plaintiff’s lawsuit against the real estate company. The reason for the different understandings of the same evidence in the first instance and the second instance is that the standards of proof are not uniform.
Generally speaking, it is impossible to draw a unified standard for the identification of legal sources, and specific cases should be treated on a case-by-case basis. Generally speaking, it can be grasped from the following three aspects: First, we must strengthen the burden of proof for those who argue for legal sources. The review of evidence must be strictly controlled; secondly, transaction customs must be respected. For example, under normal circumstances, it is impossible for the parties to agree on the technical characteristics of the goods in the transaction. In the lawsuit, the parties are required to submit evidence proving that the goods under the contract are the products accused of infringement. It is against business practices; third, we must focus on reviewing the legality of the transaction, including that the transaction process is legal and there is no case of circumventing the law or intentionally evading tort liability. Hope it will be adopted.