In the background of the construction of intelligent criminal investigation, the application of mixed reality technology in the field of criminal investigation continues to deepen. This paper analyses the user needs and problems of forensics products in the three stages of scene investigation, inference detection and court trial by sorting out the content and form of evidence in the case detection process. Based on this, this paper designs and researches forensics instrument products used in the process of evidence collection and processing. With the goal of integrating product functions, optimising the forensics process and linking application scenarios, the system innovates and forms a multispectral mixed reality intelligent helmet. In accordance with the evidence “collection - reconstruction - application” of the sequential relationship to build a smart police platform. It makes the flow of evidence information free from the massive transmission and rearrangement of paper data or traditional image data, and expands the digital application scenario of case evidence.