The examiner’s most important instrument is a trained eye. The evidence that decides a matter, however, is often beyond what the eye can see unaided:
- magnification makes the finest details visible and measurable;
- ultraviolet and infrared radiation separate inks that look identical;
- electrostatic detection reveals writing that was never written on the page — only pressed into it;
- photography records every finding for the report and for demonstration in court.
- Stand magnifiers leave both hands free to handle the document.
- Illuminated stand magnifiers accept interchangeable heads at 3×, 4×, 5×, 6×, 7.5×, 10× and 12.5×.
- The examination begins at low power and moves in on the area of interest.
The optical microscope is the principal instrument in questioned document work; critical evidence of genuineness or forgery is often invisible to the naked eye.
- Stereo microscope — a three-dimensional view of the stroke, essential for pen pressure, line sequence and tremor; a third tube allows photography through the microscope.
- Digital microscope — displays and records the magnified image.
- Comparison microscope — shows two documents side by side or overlaid; with a different colour filter on each, coinciding areas appear in a third colour.
Most handwriting examination is carried out at 10× to 50×; higher magnification narrows the field until the detail loses its context.
- Ultraviolet examination — exposes chemical and mechanical erasures, foreign adhesives and resealed envelopes, and can often restore entries that were removed.
- Infrared absorption and luminescence — distinguish inks that look identical, revealing additions made with a different pen.
- Security features — ultraviolet shows the fluorescent fibres in currency and security paper.
- Each finding is recorded precisely, including images taken through the microscope.
- Digital filters can recover obscured information on a disputed document.
- Photographic enlargements illustrate the opinion and are used to demonstrate the findings to the Court.
- The Electrostatic Detection Apparatus reveals impressions invisible to the naked eye — writing pressed through from a sheet above.
- It can establish the relative sequence of entries in ledgers, registers and medical records.
- The technique is non-destructive; the document is not altered.