Date of Award

January 2025

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Psychology

First Advisor

Kimberly Schweitzer

Abstract

In criminal trials, jurors must make a decision that will forever change the defendant’s life (Couloute & Kopf, 2018), during which jurors may consider the impact that not convicting a guilty person may have (i.e., Type II error) or if the charge is worth the crime regardless of the defendant’s guilt (i.e., Type I error). Jurors may raise their conviction thresholds if they feel a type II error is favorable to a type I error. Researchers have discovered that in cases where charge severity (e.g., Kerr, 1978) or the perceived sentence (e.g., Kaplan & Krupa, 1986) is higher, jurors shift their conviction thresholds to requiring more confidence in the defendant’s guilt to convict (Martin & Schum, 1987). However, previous literature has not simultaneously examined the relationship between charge severity, sentence severity, and the strength of the evidence. In the proposed research, participants were randomly assigned to 1 of 18 conditions in a 3 (severity of charge: first-degree murder, second-degree murder, or voluntary manslaughter) x 3 (severity of sentence: 7 – 9 years in prison, 20 – 25 years in prison, or life in prison without the possibility of parole) x 2 (evidence strength: strong or weak) factorial design. Charge, sentence, and evidence strength were hypothesized but not found to increase a juror’s conviction threshold through increasing type I error concern. The interaction between charge severity and sentence severity on a juror’s type I error concern was significant only when the defendant faced first-degree murder, compared to second-degree, but was recommended a sentence of 7 – 9 years in prison. Findings suggest that conviction threshold may be a stable trait among mock jurors. Future research should explore other extra-legal factors that could impact a juror’s conviction threshold and type I error concern.

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