The Decision Number 210/Pid.B/2005/PN.RKB examines the case of aggravated assault causing the death of the victim committed by the defendant who is having visual hallucinations. Such hallucinations belong of the categories of mental disorder, but this conclusion is merely based on a written psychological examination without any second opinion from another mental health professional. The psychiatric expert testimony (mental health professional) in the examination of this case shall be of profound significance to implicate the imposition of the sentence, which shall be viewed from the purpose of punishment. The method of analysis deployed is normative legal research by using sources of secondary data. The issues are laborated through case-based approach by comparing the Decision Number 210/Pid.B/2005/PN.RKB to the Decision Number 998/Pid.B/2006/PN.BDG by using a qualitative data analysis. The judge decides the case using the psychologist's written statements without any additional from other expert testimony of mental health proffesionals. The visual hallucination is a mental disorder that should be prescribed by a mental health professional. In the trial proceedings, an aggravated assault causing the death of the victim is proven, thereof, the judge imposen seven months and eight days imprisonment to the defendant. From the perspective of the punishment objective. Sending the defendant to a mental hospital seems to be more appropriate rather than imposing a sentence of short-term imprisonment. On the whole, the analysis concludes that the psychiatric expert testimony is greatly significant in the examination of the Case Decision Number 210/Pid.B/2005/PN.RKB, and through the purpose of punishment opinion, sending the defendant to a mental hospital is a proper final decision.