| |
| |
|
Forensics :: Document Examination
|
Optical examination by the use of different light sources and illumination techniques is a minimum standard in any non-destructive forensic document examination. If the light strikes the surface of the document at a very low angle, a grazing illumination is produced. Under oblique lighting, a different amount of lights is reflected from shadowed and non-shadowed areas on the document surface, providing greater contrast. The resulting enhancement is helpful for the detection e.g. of surface roughness due to mechanical erasure, characteristics of imprinting (intaglio printing), embossed seal impressions or indented writings. |
|
Document Examination |
| |
|
|
| Indented writings, as a form of physical evidence, are often neglected and undervalued. Information from indented impressions can provide an important link between the document and a criminal, and assist in identifying the suspect. This is especially important in the examination of signatures to detect forgery. The preliminary non-destructive examination of the document under visible light is critical. Tracing is a widely used method of simulating signatures. The produced indented impression is an objective and unambiguous sign of forgery. Indented impressions might not be visible when examined by normal reflected light. Therefore, the use of an appropriate lighting method is necessary.
A VOLPI cold light source equipped with a line converter (light line), is the most suitable lighting for the detection and examination of indented impressions on documents. The variable light intensity and the variable focusing lens of the line converter provide the necessary homogeneous and oblique light for the non-destructive enhancement of faint impressions.
Other forensic applications:
- Detection of general trace evidence
- Examination of stamped or embossed impressions
- Detection of latent footwear impressions
|
|
| |
