Foster+Freeman ESDA 2
Definition
The current-generation commercial ESDA instrument (Foster+Freeman Ltd, Worcestershire, UK), used by the FBI Laboratory, DSTL (UK), Australian Federal Police, CFSL (India), and national forensic services across the ENFSI network.
- Manufacturer
- Foster+Freeman Ltd, Worcestershire, UK
- Function
- Detects indented writing electrostatically
- Users
- FBI Laboratory, DSTL, AFP, CFSL India
- Network
- Used across ENFSI member laboratories
Common questions
What advantage does the ESDA 2 have over earlier ESDA models or manual indentation methods?+
It refines the electrostatic charging and toner development process for greater sensitivity and repeatability, recovering fainter indented impressions with less risk of damaging the original document than earlier film-based or physical impression techniques such as oblique lighting alone.
Why does an examiner keep the original document rather than working only from the ESDA image?+
The ESDA process visualises indentations but the original paper remains the primary evidence; the recovered image is a derived exhibit, and courts and further examinations may require re-testing or comparison against the physical document itself.
Can ESDA processing destroy or alter the original document?+
The technique is designed to be minimally invasive since it uses electrostatic charge and toner development rather than physical pressure or chemicals, though careless handling during mounting can still stress or damage fragile or already-creased paper.
Related terms
- 3D Optical Scanning
- Non-contact surface topography measurement using structured light or white-light interferometry to produce a nanometre-resolution height map of the document surface; an alternative...
- Birmingham Six
- Six men wrongly convicted in 1975 of the 1974 Birmingham pub bombings; their convictions were quashed in 1991 partly on the basis...
- Corona Wire
- A high-voltage wire in the ESDA instrument that deposits electrostatic charge uniformly over the Mylar surface; charge density is higher at points...
- ESDA (Electrostatic Detection Apparatus)
- A non-destructive technique for detecting indented impressions on paper caused by writing pressure. A physical ink signature on paper produces detectable ESDA...
- ESDA Lift
- The permanent transparent Mylar sheet carrying the toner-developed image of the indented writing, produced by ESDA processing; suitable for court exhibition and...
- Indented Writing
- Latent impressions produced in paper sheets beneath the writing sheet by the pressure of the pen tip; invisible under normal illumination but...
- Mylar Film
- A thin (approximately 6 micrometre) polyester film stretched over the document under vacuum in the ESDA process; it conforms to the document...
- PACE (Police and Criminal Evidence Act 1984)
- UK legislation governing police investigative powers, including the code of practice requiring audio (and later video) recording of police interviews, a reform...
- Sequence Evidence
- In ESDA casework, the determination of the relative order in which pages in a notepad were written, based on which impressions appear...