Heuristics in causal reasoning and their influence on eyewitness testimony

Abstract

In two experiments the effect of knowledge of the seriousness of an event's outcome on the estimated strength of its causes was studied. In experiment 1 participants (n=87) were shown a video of a homeless man being evicted from a police station by a police officer, during which the evictee fell. One group of participants were told that the homeless man subsequently died; the other group was told that he was uninjured. Participants who thought the homeless man had died more often blamed the policeman for the man's fall. Estimations of the force of the push were not directly related to the outcome of the event, but rather to the attribution of blame, with those who blamed the officer giving higher estimates of the force of the push. In experiment 2, before watching a revised version of the video, the participants (n=88) were assigned to one of four groups. Groups A and B were told that the homeless man had died; groups C and D were told that he had survived. In an effort to counter interference of blame attribution, groups A and C were told that the officer was to blame for the man's fall, and groups B and D that the officer was not to blame. The manipulation of guilt was not successful, but this time a significant relation between event outcome and push force was found, with those who thought the homeless man had died giving higher estimates of the force of the push than those who thought that the man had survived. As in experiment 1, those who thought the homeless man had died more often blamed the policeman and those who blamed the policeman again gave higher estimates of the force of the push. It appears then that the more tragic the outcome of a violent incident, the more blame witnesses tend to attribute to the perpetrator, and the more they tend to overestimate the amount of violence involved.     

The violent reconvictions of sexual offenders

The violent reconvictions of a sample of sexual offenders discharged from prison between 1992 and 1996 (who had not been reconvicted of a sexual offence) were examined. The hypothesis was that a proportion of these violent reconvictions would have a sexual motivation. The sample consisted of 104 adult male sexual offenders for whom detailed information regarding their violent reconviction was available. The sample was categorized according to the motivation of the violent reconviction. It was found that a proportion of the violent reconvictions were sexually motivated (12%) and that some of these had resulted from an original charge for a sexual offence. Significant differences were found between the sexual motivation and violent motivation group on the number of criminal history and victim characteristic variables. It was concluded that, in the case of sexual offenders, violent convictions might mask the true motivation of the offence.     

Death by compaction in a garbage truck

We report on two deaths by compaction in a garbage truck that recently occurred in this county. In both cases, the victim apparently climbed into a recycling dumpster to sleep, and was emptied with the contents of the receptacle into a garbage truck. Subsequent compaction of the victim with the load led to death. We also discuss several similar fatalities that have been reported to the U.S. Consumer Product Safety Commission.     

Assessing competency to waiveMiranda rights in defendants with mental retardation

Criminal defendants with mental retardation face special problems in the process of interrogation and confession, particularly with regard to the knowing, intelligent, and voluntary waiver ofMiranda rights. Despite this, little attention has been paid to empirical measurement of this form of competency in mentally retarded adults. The present research uses scales originally developed by Grisso (1981) to measure competency to waive such rights in juveniles. Two samples of mentally retarded adults, one in a sheltered workshop setting and the other composed of current probationers, were tested. Both samples scored substantially lower on measures ofMiranda comprehension than Grisso's samples of juveniles and adults. There were also differences between the samples that appear attributable to differential levels of criminal justice experience. It is concluded that the Grisso scales may be helpful in determining competency to waiveMiranda rights in defendants with mental retardation. In addition, the present data raise strong concerns about the ability of many such defendants to make intelligentMiranda waivers. Policy recommendations are discussed.     

The relationship between the soft tissues and the skeletal detail of the mouth

The estimation of mouth width and lip thickness from the skull for facial reconstruction has traditionally relied upon scant scientific research and "rules of thumb" laid down by subjective interpretation and experience. This study tested these assumptions by taking caliper and photographic measurements of mouth width and interpupillary and interlimbus distances of 96 subjects and lip thickness and teeth height measurements of 95 subjects. The most reliable indicator of mouth width was found to be the interlimbus distance, and lip thickness was positively related to the height of the teeth. There were no differences in these relationships between men and women. Standards for predicting the lip thickness from the teeth height were suggested for White Europeans and Asians from the Indian subcontinent.     

Measurement of eyeball protrusion and its application in facial reconstruction

The estimation of eyeball protrusion from the bony orbit has traditionally relied upon Wolff's theory (1976) that the cornea will be tangental to a line taken from the superior to the inferior orbital margin. This study tested this theory by taking measurements from MRI cranial images of 78 eyes of white adult subjects. Orbital depth had a significant negative linear correlation with eyeball protrusion, and protrusion of the eyeball was determined by the following standard: eyeball protrusion = 18.3 - (0.4 x orbit depth). Current eyeball position determination was shown to be as much as 3.9 mm too deep in the socket, and a practical application of this result to facial reconstruction is discussed.