Ethical implications
The question then is whether giving evidence on future dangerousness contravenes the ethical standards expected of all doctors. The answer is that it may well do so, not only because it can lead to the death of an individual, but also because the reality is that the science is so inexact that you can never safely and accurately say that an individual could not be dangerous in the future. Equally you cannot say adamantly that somebody will be dangerous in the future. Because dangerousness relies not only upon the mental state of the individual, but the circumstances in which they find themselves, this can never be an exact science, and because of its inaccuracies it is simply unethical to make such judgements. The British Medical Association (BMA) has emphasised that in its view doctors should not become embroiled in speculation about whether somebody should be subject to capital punishment.
In 1989, the US Supreme Court considered the appeal of Texas death row prisoner Johnny Penry, who was mentally retarded and reportedly had the mental age of a seven year old.
The Court noted that although evidence of Penry's mental impairment had relevance to the question of future dangerousness, it was relevant only as an aggravating factor: Penry's mental retardation and history of abuse is a two-edged sword; it may diminish his blameworthiness for his crime even as it indicates that there is a probability that he will be dangerous in the future.
Conclusion
The advice of the WPA is clear and unambiguous. Prison doctors, like other experts in forensic psychiatry cannot give objective, evidence-based judgments on future dangerousness, and such evidence must always be avoided.