Electrostatic Detection Apparatus
The Electrostatic Document Analyzer (ESDA), by Foster and Freeman, is for detecting indented writing on questioned
documents. This technique is capable of visualizing indentations on a piece of paper created by the act of writing on an overlying paper (such as commonly occurs when writing on a notepad).
ESDA works by applying an electrostatic charge to a document containing suspected indented writing. The indented writing is visualized through the application of charge sensitive toner. Indented writing (i.e., disturbed fibers) created from previously written documents on overlying pages can then be seen. In some cases, this method can be applied to develop fingerprints on documents.