Researchers of law investigate the relevant law features and identification of computer evidences, while computer scientists investigate the technological features and acquisition methods of computer evidences. As an interdiscipline of law and computer science, computer forensics must be studied from the view angle of law, computer science and their combination. The separation of them may result in the confusion of identification in law and technology in computer evidences. In this paper, relevant issues of computer forensics to criminal evidence, law and technology are jointly investigated. Since the technological methods and tools of computer forensics are important, a typical case study is presented and analyzed. Finally based on the analysis of the deficiency for the current work on law enforcement and technology, future work on the improvement of computer forensics is discussed from the viewpoint of both law and computer technology.