On the likelihood of "encapsulating all uncertainty"

Area of Science:

• Forensic Science
• Cognitive Psychology
• Legal Testimony

Background:

• Personal probabilities form forensic likelihood ratios, influenced by human cognitive biases.
• The 'helpfulness' of expert opinions is often overlooked in debates about probability correctness.
• Existing methods may not fully capture all uncertainty in forensic evidence evaluation.

Purpose of the Study:

• To analyze the subjective nature of personal probabilities in forensic likelihood ratios.
• To highlight the importance of 'helpfulness' and uncertainty quantification in expert testimony.
• To advocate for improved methods for assessing forensic evidence strength in court.

Main Methods:

• Conceptual analysis of subjective probability assignment in forensic science.
• Critique of current practices in expressing evidential strength.
• Discussion on the limitations of personal probabilities in encapsulating uncertainty.

Main Results:

• Subjective probability assignment is prone to memory, perception, and judgment errors.
• Focusing solely on probability coherence obscures the practical utility and uncertainty of expert opinions.
• Courts face challenges in evaluating expert assertions without quantified uncertainty.

Conclusions:

• Forensic likelihood ratios derived from personal probabilities are inherently subjective.
• Quantifying uncertainty within and between expert opinions is crucial for judicial assessment.
• Improved transparency regarding uncertainty is needed for reliable forensic evidence evaluation.