In 1979 Leeper, Lord and Ross asked undergraduates to complete a questionnaire dealing with capital punishment.

48 of those students were then selected for a randomized controlled trial:

a) 24 were pro capital punishment

b) 24 were anti capital pinishment

Subjects were then asked to read randomly selected studies on the deterrent efficacy of the death sentence and criticisms of those studies. Subjects were asked to rate the studies in terms of the impact they had had on their views on capital punishment and deterrence.

The chart below shows that all those who started with a pro death sentence stance thought the studies that supported capital punishment were well argued, sound and important. They also thought that the studies that argued against the death penalty were all deeply flawed. Those who held the opposite point of view at the outset reached exactly the opposite conclusion.

As Lord concluded, “Asked for their final attitudes relative to the experiments start, proponents of capital punishment reported they were more in favour of capital punishment, whereas opponents of capital punishment reported that they were less in favour of capital punishment.”