Psychiatric Expert Evidence Found Unreliable in Criminal Trials

Asst Prof Mahdev Mohan asked the Minister for Law in each year since 2011 (a) what is the number of cases in which psychiatric expert evidence has been found to be unreliable in criminal trials; and (b) whether this number is impacted by standards established by the relevant professional accreditation body.

In a case where psychiatric expert evidence is adduced, the judge may accept or reject it for various reasons. The same goes for any other expert evidence, and, indeed, any other evidence which is tendered in Court. Not all of these instances and reasons may be recorded in written judgments. The most common reason for rejecting such evidence is that the judge did not accept the expert’s evidence in the light of the specific factual context of the case. This could be because of other evidence adduced, or because a different expert's opinion was more convincing when applied to the facts and the existing state of medical knowledge, or some combination of similar factors.

The precise reasons for rejecting psychiatric expert evidence on purely factual grounds thus depends on the factual context of each particular case. They do not necessarily imply any fault on the part of the expert. For this reason, the number of such rejections are not necessarily related to the professional standards governing psychiatrists.

There have been cases where the Courts have said that they rejected an expert's opinion because he or she failed to meet the minimum standards and objectivity expected of an expert witness. For example, in the case of Mehra Radhika v Public Prosecutor [2015] 1 SLR 96, the Chief Justice observed that the expert psychiatric evidence adduced in that case was "patently lacking in objectivity" and was "plainly erroneous". The Chief Justice also observed that the expert in that case "did not give … the sense that he had even a basic conception of the responsibility he owed the Court when he put himself forward as an expert".

The proposed amendments to the Criminal Procedure Code will set out the duties of an expert witness, whether psychiatrists or otherwise, consistent with existing norms. A panel of psychiatrists will also be set up, such that members of this panel will be allowed to give psychiatric expert evidence in criminal cases.