Accuracy and reliability of forensic handwriting comparisons

Area of Science:

• Forensic Science
• Document Examination
• Psychology

Background:

• Forensic handwriting examination is critical for legal proceedings.
• Assessing the accuracy and reliability of forensic document examiners (FDEs) is essential.
• Previous studies have indicated potential variability in FDE performance.

Purpose of the Study:

• To evaluate the accuracy and reliability of conclusions made by practicing FDEs.
• To identify factors influencing the performance of handwriting comparisons.
• To quantify error rates in forensic handwriting analysis.

Main Methods:

• A large-scale study involving 86 practicing FDEs.
• Each FDE conducted up to 100 handwriting comparisons on 180 distinct sets.
• A five-level conclusion scale was used to categorize findings.

Main Results:

• False positive rates were 3.1% for non-mated samples and 1.1% for mated samples (false negatives).
• Error rates were significantly higher for non-mated samples from twins (8.7%) compared to non-twins (2.5%).
• Training duration correlated with performance: less training led to higher error rates but more definitive conclusions; more training resulted in fewer definitive but more accurate conclusions.

Conclusions:

• The study quantifies error rates in handwriting comparisons, revealing specific challenges like distinguishing samples from twins.
• Formal training duration impacts FDE conclusiveness and accuracy.
• Writing style (cursive vs. printing) did not affect error rates.