Witnesses rarely testify at trial in China and the courts routinely rely on investigative dossiers to determine the guilt or innocence of the defendant. Shielded from external scrutiny, relatively little is known about how these investigative dossiers are constructed and whether they are truly reliable. To understand the construction process for police cases, ethnography, semi-structured interviews and content analysis of the dossiers have been conducted to explore the formation of evidence during the police investigation. This article reveals that the constructed evidence is subject to manipulation and distortion designed to enhance the incrimination of the accused. With a lack of the functional equivalence in defence construction required to challenge the facts presented in these dossiers, the current criminal justice system in China is structurally weak and fails to function as a truth-finding process.