Lead isotope ratios for bullets, forensic evaluation in a Bayesian paradigm

Area of Science:

• Forensic Science
• Analytical Chemistry
• Statistics

Background:

• Forensic science relies on evidence examination for criminal cases.
• Technological advancements drive forensic science.
• Bayesian statistics and logical reasoning are increasingly accepted for evidence evaluation.

Purpose of the Study:

• To trace lead fragments of unknown origin to a specific ammunition source.
• To apply Bayesian statistics and lead isotope ratio analysis for forensic casework.
• To provide a quantitative measure of evidence value for judicial deliberation.

Main Methods:

• Analysis of lead isotope ratios in small arms projectiles (caliber .22).
• Development of a Bayesian statistical approach.
• Calculation of the likelihood ratio to quantify evidence strength.

Main Results:

• The study demonstrates a method for tracing lead fragments using isotopic composition.
• Bayesian interpretation of lead isotope data is suitable for guiding court conclusions.
• The likelihood ratio effectively measures the evidential value.

Conclusions:

• Lead isotope ratio analysis within a Bayesian framework is a valuable tool for forensic investigations.
• This approach aids in linking physical evidence to its source.
• The likelihood ratio provides a clear metric for courts to assess evidence.