Four different vignettes were created based on the M'Naghten murder case. One vignette contained no reference to the mental disorder of the accused. Another indicated that the accused had a history of mental illness. The third stated that the accused was politically active without indication of mental illness. The fourth described the accused as being both mentally ill and affiliated with political extremism. Twelve different subjects received each of the four vignettes and on the basis of these, expressed their opinion on the possibility of the accused's being found guilty. Important differences emerged from the four groups, indicating that the opinions of the law students could be influenced. It is highly likely that judges' opinions in real situations are similarly influenced by exposure to biasing information. 6 charts and 12 references are given. (Author abstract modified)