PLANS to use more computers for police work would put an extra 400 officers on the streets to fight crime. A comprehensive computer strategy costing more than $500 million would save at least 569 administrative and support posts, cutting staff costs by at least $131 million a year. If the strategy is implemented, around 400 officers would be freed for patrolling the streets, thereby providing a better service to the community. The new Information Strategy would develop five major groups of computer systems to meet the police force's needs and a communication network to link new systems to those already in place. It would cost taxpayers a total of $526 million, spread over a five-year period ending in the financial year 1997-98. It is understood the police believe Information Strategy would benefit all levels of the force, from commanders to constables on patrol. The system would cover criminal investigations, force operations and administration. Major benefits for introducing the system include improvements in the operational efficiency and effectiveness of the police force, particularly in the fight against crime, through better utilisation of police officers, and faster and more efficient retrieval of information. It would also help to release police officers from routine administrative duties to constabulary functions and ''front-line'' operational roles, as well as reduce time in processing cases at police stations. Among the proposals is the Force Criminal Investigation Support Systems under which a computerised crime records programme would be installed for the maintenance and retrieval of records. The proposed system would cover the handling of documentary exhibits at the Commercial Crime Bureau, and the storage of files and documents at the Narcotics and Criminal Intelligence Bureaus. These records would be retained in the system for a period no longer than necessary for operational or legal use. Generally, documentary exhibits would be kept until an investigation was completed, while case files would be kept for 10 years. To ensure data protection, the police require that system access be granted only on a need-to-know basis. For instance, users at administrative locations would not be given the right of access to operational or criminal applications, and vice versa. Stringent security measures including three levels of security would be incorporated to deter unauthorised use. The force's Information Strategy Committee would monitor progress. Reviews would also be conducted to ensure that the identified benefits were achieved.