A large number of frequent criminal offenses in Modayag sub-district make the police must act quickly and appropriately in handling the cases. One of the obstacles faced by the police is the number of articles violated by the suspects, so that the police must choose the appropriate articles in the Criminal Code and in accordance with the crimes committed. This action is less effective because it takes time in searching process and there might be missing passage. This expert system was made in order to help the Modayag Cops to give right decision. This decision was taken based on the accordance with the application of particular articles that were derived by the Criminal Code during the inspection. Case-based reasoning with K-nearest neighbor and certainty factor in this system used prior experience in similar cases to solve new cases and forward chaining for rule based searching and calculation of a certainty factor method to determine the exact compatibility case with a related article. The result of this application in the form of articles and sanctions related to criminal acts committed the suspect also the presentation of the method used.

Keywords: Expert System, Criminal Code, K-Nearest Neighbor, Certainty Factor.