http://www.apa.org/monitor/jun05/ethics.aspx If you can articulate the appropriateness of your decision to administer the WAIS III versus the WAIS IV using sound scientific reasoning, based on your knowledge of the relevant literature and professional experience as a psychologist, then it is appropriate to do so. In fact, it may be in the individual's best interest to do so. As a note, I was trained with and use the WAIS IV in forensic practice, but I recognize some unique and interesting aspects of the WAIS III and have thus taken it upon myself to learn the measure. In the end, we must be guided by empiricism, lest we fall prey to passion and unreasonable opinion. My .02 on the matter.