An expected cost model of eyewitness identification

Area of Science:

• Forensic Psychology
• Legal Psychology
• Decision Analysis

Background:

• Eyewitness identification is crucial for criminal investigations but prone to errors.
• Evaluating the effectiveness of different eyewitness identification procedures is complex.
• Existing methods may not fully account for the costs associated with accurate and inaccurate identifications.

Purpose of the Study:

• To present an expected cost model for evaluating eyewitness identification procedures.
• To quantify the performance of identification procedures in achieving police investigation goals.
• To analyze the impact of procedural reforms on identification accuracy and costs.

Main Methods:

• Development of an expected cost model for eyewitness identification.
• Application of the model to analyze five major procedural reforms (showups vs. lineups, filler similarity, administrator influence, lineup instruction, presentation format).
• Analysis considering simultaneous outcomes: suspect identifications, filler identifications, and rejections.

Main Results:

• Procedural superiority conclusions are contingent on the prior probability of guilt and relative costs of identification outcomes.
• Varying the costs of filler identifications and rejections can alter findings on procedural effectiveness.
• The model quantifies how reforms impact the balance between accurate and mistaken identifications.

Conclusions:

• The expected cost model provides insights into optimizing eyewitness identification procedures.
• Legal systems can reduce expected costs by adjusting conditional probabilities, outcome costs, or prior guilt probability.
• This framework aids in minimizing errors and improving the reliability of eyewitness evidence.