Serial theft case linkage based on a two-step cumulative probability model

At present, serial theft case linkage remains at the stage of empiricism. In order to overcome this subjective arbitrariness, this study proposes using a ‘two-step cumulative probability model’ for investigation. In the first step, based on expert grading method, the opinions of 99 policemen were combined to quantify the serial theft case characteristics. In the second step, when a new case occurred, the characteristics of it were compared with the characteristics of each serial theft case, and the corresponding probabilities were added according to the calculations of the second step; when the accumulated points exceeded the threshold, we considered concatenating the new case with the corresponding serial cases. The results demonstrated that the average accuracy of the two-step cumulative probability model was 87.5% and that the average response rate of the irrelevant case (control group) was 12.3%. We concluded that the two-step cumulative probability model could assist in criminal investigations.