Alterations, Erasures, Obliterations and Indented Writing

In one line

A document that has been changed usually carries the record of the change, and the examination is about finding it.

In the wording a student can write in an exam: a document may be altered by addition, by substitution of a page, by erasure, whether mechanical or chemical, or by obliteration, and each leaves signs that can be detected by physical and optical examination; mechanical erasure disturbs the paper fibres and can be seen by oblique and transmitted light; chemical erasure changes the fluorescence of the paper under ultraviolet light; an obliteration can often be read through by infrared examination, because inks that look alike in visible light differ in their infrared absorption and transmission; and indented writing, being the impression left on a sheet lying below the one written on, is recovered by oblique lighting or by electrostatic detection.

Addition and interlineation

What it is. Words, figures or a whole line written into a document after it was made: a nought added to a figure, a name inserted in a will, a clause added to an agreement.

The signs. Crowding of the writing to fit the space; a different slant, size or spacing; a change of alignment; the writing running around an existing feature; a different ink; and a difference in the writing itself where a second hand was used.

How it is examined. Magnification, then examination of the ink under ultraviolet and infrared, because a different ink is the commonest proof.

And the sequence of strokes. Where an added stroke crosses an existing one, magnification can sometimes show which was written first, from the way one line lies over the other.

Erasure

Mechanical erasure, by a rubber, a blade or an abrasive.

Its signs. Disturbance of the paper surface, seen as roughened or lifted fibres under oblique light; thinning of the paper, seen under transmitted light; loss of the printed ruling or of a watermark detail; and, where writing is added over the erased area, spread of the new ink into the disturbed fibres, producing a feathered stroke.

Chemical erasure, by a bleaching or oxidising agent.

Its signs. A change in the fluorescence of the paper under ultraviolet light, usually a darker or differently coloured patch corresponding to the treated area; a change in the colour of the paper; and often a residual trace of the original writing.

What can be recovered. Sometimes the original writing, from residual traces made visible by ultraviolet or infrared examination or by chemical means.

Obliteration

What it is. The covering of writing by overwriting, by scribbling over it, or by a correction fluid.

How it is read.

Infrared examination is the principal method. Two inks that appear the same colour in visible light may differ in their absorption and transmission of infrared, so one may become transparent to the infrared camera while the other remains dark, and the covered writing then reads through.