Deciphering Obliterated Signatures using IR Imaging and Reverse Illumination Technique

Abstract

Obliteration of signatures in questioned documents poses a significant challenge to forensic document examiners, especially when layered with multiple interfering substances such as scribbled pen strokes and correction fluid. This study underscore the efficacy of ultraviolet (UV) and infrared (IR) imaging, using the Docucenter Nirvis system integrated with PIA 7000 software, in deciphering obliterated signatures. Two illumination approaches, front-side and reverse-side were employed. While front-side illumination failed to reveal the obscured content, reverse-side illumination combined with appropriate IR filtering and digital processing enabled successful retrieval of the original signature. The results underscore the importance of reverse illumination as a viable and essential technique in the forensic examination of tampered documents.

Introduction

Obliteration refers to the deliberate act of making written content unreadable to conceal or destroy original information. In forensic document examination, common obliteration methods include overwriting, smudging, using correction fluid, scratching, or applying chemicals. These techniques aim to hide crucial information, such as signatures, which may hold legal significance.

In this case study, a partnership deed was submitted to a forensic lab where one partner’s signature had been deliberately obliterated using a two-step method:

1. Scribbling with pen strokes.

2. Applying correction fluid over the scribbles.

This dual-layer obliteration posed a significant challenge for decipherment.

Laboratory Examination:

Two forensic techniques were used:

1. Front-Side Illumination:

   • UV and IR light revealed the layers of obliteration but failed to uncover the original signature due to heavy masking.

2. Reverse-Side Illumination:

   • Using the LumiIR filter, the document was illuminated from the back.

   • A reverse image of the obliterated signature was successfully captured.

   • This image was then digitally flipped to reveal the original signature clearly.

Conclusion

Reverse-side infrared (IR) illumination, combined with advanced imaging and digital processing, proves to be a powerful and non-destructive technique for deciphering signatures hidden beneath multiple layers of obliteration. While front-side examination often fails due to ink density and overlap, reverse illumination exploits the varying optical properties of inks, making concealed content visible. The integration of IR light with digital enhancement tools ensures accurate recovery of original writings without damaging the document. The results support earlier studies showing that reverse-side imaging is often successful in revealing hidden or covered text.

References

[1] Kelly JS, Lindblom BS. Scientific Examination of Questioned Documents. 2nd ed. Boca Raton: CRC Press. [2] Ellen D. The Scientific Examination of Documents: Methods and Techniques. 3rd ed. Boca Raton: CRC Press. [3] Aginsky VN. Forensic science applications of infrared luminescence in the examination of documents. J Forensic Sci. 1993; 38(5):1134-1156. [4] Cantu AA. Chemical and physical methods for examining document alterations. J Am Soc Questioned Document Examiners. 1995;1(1):27-36.

Copyright

Copyright © 2025 Rajat Choudhary, Pankaj Mohan, Anushri Dutta, Meenakshy R V. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.