New Study Reveals Outsized Role Manner-of-Death Determinations Play in Criminal Trials

A new study has been published that adds to a growing body of literature on the influence certain types of evidence have on jurors. It has been a topic of conversation in legal circles about the outsized role manner-of-death determinations play in criminal prosecutions. This new study continues that conversation.

Jeff Kukucka and Oyinlola Famulegun’s study builds upon what we already know: contrary to jurors’ beliefs that forensic experts are objective, such experts are susceptible to cognitive bias.

Recently, Itiel Dror, Kukucka, and others demonstrated that cognitive bias can even affect manner-of-death determinations. I discussed those studies here and here.

The responses to Dror et al.’s work were mixed, but those who were critical of the findings explained that manner-of-death determinations were not scientific and were primarily used for public health statistics.

This raised a question: manner-of-death determinations are often offered as evidence in courtrooms. In Indiana, for example, it is rare in a criminal case involving a homicide not to hear testimony regarding the manner of death. So if critics now claim manner-of-death determinations are not really scientific, how do jurors view them?

Answering this question was one of the aims of Kukucka’s study. The other aim of the study was to determine whether extraneous information affected jurors’ views of the strength of manner-of-death determinations as evidence.

The study was designed as follows. Kukucka used a fact pattern similar to the facts surrounding Melissa Lucio’s case: a mother was accused of murdering her child. Participants in the study were divided into four groups:

• one group read testimony from a medical examiner who opined that the manner of death was by accident, and the group was told that the mother was an affluent Caucasian woman;

• a second group read the same testimony from the medical examiner as the first group, but this group was told that the mother was an underprivileged Latina woman;

• a third group read testimony from a medical examiner who opined that the manner of death was by homicide, and the group was told that the mother was an affluent Caucasian woman; and

• a fourth group read the same testimony from a medical examiner as the third group but was told the mother was an underprivileged Latina woman.

The study revealed that the manner-of-death determination had a statistically significant effect on whether the jury found the defendant was guilty. This finding was true regardless of the class and ethnic background of the defendant. The study participants all rated the medical examiner’s testimony as highly scientific, highly credible, and highly convincing, regardless of the examiner’s determination as to the manner of death. The results of the study were so convincing Kukucka found the “medical examiner’s opinion was practically dispositive on trial outcomes.”

PRACTITIONER TIPS: In light of the findings of his study, Kukucka made several recommendations, two of which should be considered by practitioners handling cases with manner-of-death determinations. Kucka recommends either the complete exclusion of testimony regarding the expert witness’s opinion as to the manner of death, or eliciting testimony at trial from the expert that manner-of-death determinations are just opinion and should not be considered as “scientific” evidence.