ESDA® is the leading technology for detecting indented writing on questioned
documents. ESDA® works by creating an invisible electrostatic image of indented
writing, which is then visualised by the application of charge sensitive toners.
The sensitive imaging process reacts to sites of microscopic damage to fibres at the
surface of a document, which have been created by abrasive interaction with
overlying surfaces during the act of handwriting.
ESDA® is the ideal forensic tool. As well as being simple to operate, it produces positive,
life-size transparencies of indented writing without damage or contamination to original
documents and without interference to other forensic tests, and documents may be
processed repeatedly without loss of sensitivity.
The Cascade Developer
This is the standard image development system for ESDA and consists of carrier
beads coated with specially formulated toner powder that becomes tribo-electrically
charged when in contact with the beads. When ‘cascaded’ over the electrostatic
image of the document the charged toner becomes dislodged and is attracted to the
areas of indented writing. The beads are recovered from the collection tray on the
side of the instrument for reuse. Loose toner which may fall on to the background
is recaptured by the carrier beads and removed to maintain a good