Misidentifications of alphanumeric characters in serial number restorations

ABSTRACT

Chemical etching has long been established as a reliable means of recovering defaced characters such as serial numbers. Although successful restorations can present clearly defined characters, a preliminary assessment of proficiency test results shows varied participant interpretations of samples marked with the same characters. Thus, a study was completed to determine if specific alphanumeric characters are more likely to be misidentified, comprising a practical exercise and analysis of 16 compiled proficiency test results. The practical exercise involved 64 steel plates stamped with six randomized characters that were removed and chemically restored. Participants individually assessed the plates and provided their interpretations. A total of 39 participants of various backgrounds and experience in serial number restorations were used in this study. After comparing participant interpretations with the ground truth, characters more prone to be misidentified were determined. The proficiency test results showed that the most frequently misidentified characters were the letters B and N, among a limited set. Whilst the practical assessment found a notable increase in misidentifications for the letters G, Q and S. Interestingly, none of these characters were used in the proficiency tests. It is hoped that the results of this study raise awareness for forensic examiners undertaking restorations.

KEYWORDS:

• Serial number
• restoration
• interpretation
• misidentification
• alphanumeric characters

Acknowledgments

Special thanks to Eric Murray for his ongoing commitment to the development of science in Australia through the Australian & New Zealand Forensic Science Society (ANZFSS) NSW Branch Eric Murray Professional Achievers Award. Further thanks to Daniel Paine and Sam Bottrill for all their support with this research.

Disclosure Statement

No potential conflict of interest was reported by the authors.

Notes

1. Edcon Steel 4140 Round Bar Data Sheet – https://www.edconsteel.com.au/store/storage/pdf/4140.pdf.

2. Edcon Steel 300 Plus Square Bar Data Sheet – https://www.edconsteel.com.au/store/storage/pdf/300plus.pdf.

3. Note: Copper Chloride Working Solution is a variant of Fry’s solution, comprising of 36% w/v Copper (II) Chloride, 48% v/v Hydrochloric Acid and 40% v/v Water. Traditional Fry’s Reagent comprises of Copper (II) chloride 90 g, Hydrochloric acid 120 mL, Deionized Water 100 mL.