Examinations can be undertaken to determine whether documents may have been produced on the same typewriter/printer. It can be possible to demonstrate that documents purportedly originating from a variety of different sources have actually been created by a single printer.

Throughout a typewriter or printer's life, it will experience use and abuse which may cause defects in the typewritten/printed product by way of damaged elements, elements containing pressure faults, misaligned elements, certain extraneous marks on the document, non-printing of certain components, defects on the application of ink/toner to the paper etc.

From the observation of an accumulation of such defect characteristics which are found to be common in two documents, the weight of evidence can lead to the positive identification of a single typewriter/printer being responsible for the production of documents under examination. The potential change of defects over time can also be examined with respect to dating typewritten/printed material.

The printing on a multipage document can also be microscopically examined to determine whether a page substitution has occurred.

Documents can be examined for security printing which is invisible to the naked eye. Security printing is commonly applied by printers and copiers and by examining the same, it can be demonstrated that documents have originated from a single source.