Electrostatic detection device

ESDA (from ElectroStatic Detection Apparatus), is the trade name of a piece of equipment manufactured by Foster & Freeman Ltd (UK). The device is commonly used in questioned document examination, to reveal latent indented impressions on paper which may otherwise go unnoticed. It is a non-destructive technique (will not damage the evidence in question) thus allowing further test to be carried out. It is a sensitive technique, and has been known to detect the presence of fresh fingerprints. In fact, the device was originally intended for this purpose and its use for indented writing was a fortuituous, but valuable, accident.

In general, when writing is fashioned on a sheet of paper resting upon other pages, the impressions produced are indented onto those below. The degree of indentation will vary depending upon the nature of pen used (harder tips are more effective), the degree of pressure applied to the instrument, the softness of the paper and/or writing surface, etc. The indentations in the paper may be detected using the ESDA, thus providing a transcript of the original entry or allowing a match of the original document to its source (such as a ransom note or threatening letter) back to a particular notepad.

For instances where two or more handwriting styles can be found mixed into a single document, and features of one handwriting style depart from the features of another's, ESDA can help reveal the differences in pressures employed between the individuals responsible for the writing samples otherwise unified on a single exemplar.

External links

• A more detailed descripton of the process

• A detailed presentation followed with experiments, of how the ESDA device is useful in Forensic Handwriting Examination (in Greek).

• Foster & Freeman Ltd (UK): manufacturer of the ESDA, ESDA2 and ESDA-Lite