The Venezuelan penal system is enriched by the science of psychology, which is responsible for studying man’s behavior within a society. It is a science that connects with penal law and is increasingly adhered to in the face of the demands and differences that converge on a human being within a society. Therefore, the penal system has not remained behind regarding the advance and development of this discipline of knowing, because the latest reform of the Organic Code for Penal Process established bases for participation of the forensic psychologist in the justice administration process, a person who is able to emit judgments on facts regarding the acts that man performs -conscience, willingness and mental clarity- as causal for attributing the punishable deed. Therefore, it is necessary to analyze the intervention of the forensic psychologist in determining mental illness as cause for impunibility. Research methodology includes description and analysis of impunibility and psychology from a legal and forensic perspective.