The investigation makes a theoretical proposal by using the techniques of Witness Credibility (CBCA), Hare s PCL-R and Global Evaluation System (GES) in sexual aggressors. A bibliographical revision of the forensic psychology was made, along with sexual aggressors, paraphilias, psychopathy, PCL-R, Witness Credibility, and GES. It was made with a qualitative study with a descriptive investigation design while information was gathered by a discussion group. In results it was found that is if vital importance before applying the proposal, revising the documents brought to the process, also it was found that the no autoincrimination principle must be respected and most important, the principal utility of this proposal for the sexual specialized relapsing aggressors. In conclusions it is proposed that this investigation should be used among other psychometric tests in order to validity and reliability to be risen, and more investigations along with validations should be done so this proposal to be improved, developed and perfected.