By Savannah Peters

In the year 1990, in the state of Mississippi, the body of 3-year-old Courtney Smith was discovered floating in a pond in Noxubee County. She had disappeared from her bed two days prior, which she had shared with her two sisters. The girl had been sexually assaulted and murdered, and marks that resembled bite marks were found on her body. Her 5-year old sister identified a man named Levon Brooks as the person she thought she saw take her sister away. Brooks had been the ex-boyfriend of their mother, and as such had initially become a suspect in the case. In January 1992, he was found guilty of the crime based both on the sister’s testimony and the expert testimony of Dr. Michael West, a forensic odontologist. Dr. West examined the bite marks on Smith’s body and claimed with certainty that the marks matched two of Brooks’ teeth.  

A couple of months after Brooks’ trial, another body was discovered in Noxubee County. It was that of Christine Jackson, another three-year-old who had been sexually assaulted and murdered, similarly to Smith. In this case, no less than 19 supposed bite marks were found on the girl’s body. Again, suspicion was placed on a familiar face; the boyfriend of the girl’s mother called Kennedy Brewer. The similarities between the two cases didn’t stop there, however. Again, Dr. Michael West was appointed to the case, and he said the following: “The bite marks found on the body of Christina Jackson were indeed and without doubt inflected by Kennedy Brewer.” His testimony was key in the conviction of Brewer, as it was in Brooks’ case. 

Contrariwise to Brooks’ trial, Brewer’s defense attorney hired another forensic odontologist to challenge Dr. West’s claim, Dr. Richard Souviron. He criticized the technique that Dr. West chose to use, namely ‘direct comparison’. In this technique, a mold is made of the suspect’s teeth which is then placed onto the bitemarks to see if they match. This mold can be moved around as desired to match the teeth with the bitemark, and Dr. Souviron along with many other odontologists believed this technique to be unreliable. In fact, Dr. Souviron didn’t believe the marks found on the girl were bitemarks at all. The imprints would imply that for all the 19 bites, only upper teeth would have to be used, and while this could happen once by coincidence, the fact that it happened 19 times would mean these marks weren’t bitemarks at all. Despite Dr. Souviron’s testimony, who was found to be too “flippant” according to the judge, Brewer was sentenced to death.  

It wasn’t until much later that DNA evidence recovered in 1992 would lead to the exoneration of both Brooks in 2001 and Brewer in 2008. This DNA belonged to Justin Albert Johnson, who confessed to both crimes but denied having bitten either girl. This statement is consistent with Dr. Souviron’s conclusion about the marks not being bitemarks as well. Rather, as it turns out, the marks found on the girls’ bodies were insect bites. 

These cases both demonstrate the overconfidence bias. This bias occurs when individuals report being more confident in their judgments than is called for by their actual accuracy (Miller et al., 2015). Only a small relation is found in the literature between confidence and accuracy, too little to claim that the confidence of an expert predicts their accuracy. However, a display of overconfidence is related to other people’s judgments of the expert. This is described by the confidence heuristic model, which shows that people judge confident individuals as being more accurate (Miller et al., 2015). 

The overconfidence bias is clearly seen in the statements of Dr. West, who claimed to know with certainty that the examined bitemarks belonged to Brooks and Brewer. He did not report the limitations of his technique to the court either. Furthermore, his overconfidence caused the judges to find his testimony preferable to that of Dr. Souviron in Brewer’s trial, which resulted in the conviction of the latter. 

Evidently, Dr. West’s overconfident statements were not inconsequential as they managed to dramatically alter the lives of two innocent people. Brooks spent 16 years in prison, and Brewer spent 15 years in prison. In both cases, Dr. West’s testimony played a key role in the later convictions. The cases of Levon Brooks and Kennedy Brewer clearly show that even someone who is regarded as an expert in their field may be prone to error and bias. Realizing that everyone is prone to bias is important, yet not enough to completely eradicate their effects. 

References 

Miller, D. J., Spengler, E. S., & Spengler, P. M. (2015). A meta-analysis of confidence and judgment accuracy in clinical decision making. Journal of Counseling Psychology, 62(4), 553–567. doi:10.1037/cou0000105 

Kennedy Brewer. (n.d.). Innocence Project. Retrieved from https://innocenceproject.org/cases/kennedy-brewer/ 

Levon Brooks. (n.d.). The Innocence Project. Retrieved from https://innocenceproject.org/cases/levon-brooks/