Typewriter and Printer Analysis
Criminals may type a document like a ransom note or a threatening letter in the mistaken belief that, unlike handwriting, typed script cannot be readily identified. However, the forensic document examiner may well be able to extract some valuable evidence from a typed document. The advent of modern office technology has brought about some important changes in this kind of work. Most documents today are produced on modern laser printers and photocopiers that are difficult to distinguish from one another. Manual typewriters are much more individual as machines and the investigator can glean far more information from a manually typed document than from a printed document.
While it is unusual to find a manual typewriter in a modern office, some people still keep these machines for personal use. They are also still found in some developing countries. Therefore, the forensic examination of typewritten documents can still be important. A manual typewriter has many moving parts that tend to deteriorate over time and introduce tiny faults into a printed document. The document examiner looks for these faults when trying to tie a document to a particular machine that may already be available as an item of evidence, perhaps having been found at a suspect's address.
Typewriters produce letters with standard typefaces, but the size, shape, and styling of the letters may vary with the make and model of the machine. There are databases with identifying information on the letters produced by different typewriters and a comparison may be informative. If a suspect machine is present, the investigator will use it to produce a comparison document to see how closely it resembles the questioned document. He or she will try to reproduce the conditions, such as paper, age of the typewriter ribbon, and so on, that were used to produce the original. A side-by-side visual comparison of the two documents may be sufficient to decide whether they have been produced by the same machine.
Manual typewriters in which the individual characters are fixed to the end of a type bar can produce a number of individual characteristics, such as misaligned or damaged letters, as the letters begin to age. There may also be subtle variations in the pressure applied to the page by different keys which will show up as differences in how heavily inked the letters are. The investigator will also look for tiny variations in the spacing between the letters.
Electric typewriters are more modern than manual machines and the letters are produced with either a daisy wheel or a golf ball. The most important feature of these two elements, from a forensic point of view, is that they start to deteriorate with increased use. Faults develop which are transferred to the typing on the paper and the examiner may be able to detect tiny flaws within the print. These same flaws will show up in a comparison document produced with the same machine and so can be used to help identify it.
Typewriter ribbons can be quite informative to the document examiner. The letters are stamped out on the paper as an image of the ink of the ribbon. Therefore the ribbon may bear an image of some of the letters and words of the document. The roller or platen of the typewriter may also contain information, because an image of the text may have been transferred to it. Tiny imperfections in the roller may also be transferred onto the document. Analysis of carbon paper, used to create copies, and correction papers may also reveal fragments of text from the document under investigation.
In most offices and homes, typewriters have now been replaced by printers. The first printers, which are not much seen now, were dot matrix printers. These were then superseded by ink jet and laser printers. It is relatively easy to determine whether a document was produced with a dot matrix, ink jet, or laser printer. Beyond this, however, it can be very hard to distinguish one make and model of printer from another. Printers are mass produced and they have fewer moving parts than typewriters which makes it hard to extract much identifying evidence that can tie a document to a particular machine. However, there may be tiny scratches on the drum of a laser printer which may be transferred onto the document.
Sometimes the investigator wants to determine whether a document is an original or a photocopy. Modern photocopiers have much the same mechanism as a laser printer. Minute faults on the camera lens, drum, or other part of the mechanism may be transferred onto the document. Similarly, specks of dust on the glass sheet where the paper to be copied is placed may transfer so called "trash marks" onto
the copy. In this way, it might be possible to match a copy to a particular photocopier.
It was reported in late 2004 that, in an effort to assist governments trying to combat crimes such as counterfeiting, some color laser printer and copier manufacturing companies, such as Xerox, have begun utilizing technology that prints faint information, including the serial number of the machine, on every document it prints in small yellow dots that are virtually invisible to the naked eye. Though this technology is useful to those trying to combat crime, it also has privacy ramifications.
