The author traces the evolution of computers and computer-based technologies and then discusses the applications of computers in American criminal justice of the 1990's. Computer applications are discussed under the topics of data-based management, organizational communications, computer-assisted diagnosis/education/training, computer-assisted monitoring of offenders, and computer-related crime. Evolving technologies, including artificial intelligence and virtual reality, are discussed in terms of their future applications. The author advises that three emerging computer technologies have significant implications for criminal justice in the 21st century: artificial intelligence (AI), virtual reality (VR), and biomedical research into direct brain-computer linkage. With AI, it may be possible for users to interact verbally with computers, inputting data and instructions without having to touch a keyboard. Computers will clarify what they are supposed to do by asking the user questions. Computers will be able to provide users with verbal output information. Emerging AI technology will also make it possible to develop network linkages among currently incompatible databases. These advances will be incorporated into criminal justice communication and crime analysis capabilities. Increasingly, crime scene evidence will be collected and analyzed in the field or at crime scenes. Corrections will use AI to manage its huge offender data systems. Regarding VR technology, witnesses may be allowed to recall subconscious or suppressed memories. Conceivably, it may even be possible to question a subject and obtain accurate perceptions of facts and events without consent; such use would have obvious constitutional implications. The integration of artificial intelligence, virtual reality, and computer-assisted instruction may also have great potential for offender therapy and rehabilitation. 10 notes and 50 references