A huge proportion of crime relates to acts of fraud. This is the deliberate deceiving of people or organisations for personal gain. Consequently, a significant part of forensic science has to do with the analysis of documents.

Handwriting is an obvious area to investigate. There has been a great deal of research into the analysis of handwriting and signatures in order to match the writing on a receipt, letter or other piece of evidence with the handwriting of possible suspects.

If a typewriter is used, it can be matched. No two typewriters strike paper in exactly the same way. They too can be 'fingerprinted'. Laser printers, as they age, get small signs of wear and tear which can show up as tiny dots in the same place on every page. It is possible to use infrared technology to detect documents which have been changed. For example, a financial record which has been fraudulently altered may look fine to the naked eye. Using an infrared scan of the document, you can see the original details and proved that it has been altered.
And so the methods go on. It is a very complicated field.

Sometimes, even documents which have been burnt can be read. A chemical solution called polyvinyl acetate is sprayed on so the document can be flattened. They are then photographed under infrared illumination to reveal original writing which had been blackened by the fire.

Handwriting contains a combination of characterises which are unique to the writer. Forensic scientists look these tell-tale signs when he or she is trying to identify handwriting in letters, wills, receipts, suspected forgeries, cheques and, of course, ransom notes.

This is not the same as using handwriting to assess someone's personality. That is an entirely different field - one which many people consider totally unscientific. Forensic document experts are looking at the physical similarities. They leave the personality profiling to others!

On the left are four ways I sign things. We do not have only one signature. Can you see characteristics which a forensic scientist would find common? The way I do the 'y' and the 'L' are two obvious ones. Anything else?

The ransom notes I have written on the left are done to enable you to explore what details you could look for in a sample of writing. The first is my natural writing. The second is my natural printing. The third is me trying to disguise my handwriting. How well did I do?

Investigators look closely at the following characteristics when they are examining handwriting:

* the form of the handwriting, such as the shapes of the letters and their slant, angles, connections, and curves. That is, the way the lines are used to make the letters.
* the line thickness which comes from the type of writing instrument used and the pressure used while writing with that pen or pencil.
* the arrangement on the page, including spacing, alignment and formatting.
* any unique punctuation - such as my 'pm'  and the ':' in the time, and the dollar amount.
* any ornaments such as circles as the dot on an i.
* the amount of space between letters and words.
* how the i's are dotted and the t's are crossed.
* spelling, punctuation, and grammar. I did get that right, didn't I?
* the actual content including the phrasing of the request.

When a forensic scientist suspects forgery, one of the first things he or she does is to get a handwriting sample from the suspect. This sample is called an exemplar.

Usually, the scientist tries to get the suspect to write the same text as the forged document with the same type of writing instrument as was used for the forgery. That may be a pencil, ballpoint pen, fountain pen, felt marker or any of the modern variations of these.

The forensic investigator dictates the words for the sample to the suspect. That forces the suspect to use their own spelling and punctuation. The sentences are dictated several times, changing the speed for each test. In this way, the forensic scientist has a better chance of getting a normal handwriting sample from the suspect. The suspect just doesn't have the time to think through what to do, as well as work out what the investigator is playing at.

When trying to disguise handwriting, most people will write smaller or larger than they normally do. They may also try to change the slant of their writing. They may print instead of write, or they may change the hand they write with. But a skilled forensic investigator knows all of this. They have seen it all before!

Testing the theory

Dictate my ransom note three times to each of three 'suspects', including at least two adults, asking them to do the same as I did. Write naturally, print and then try and disguise their writing. Then ask them to do the disguised one again while you dictate as fast as they can write.

Using the data you have now collected from your three 'suspects', make a list of all the details you would look for to assess whether a ransom note came from one of the suspects you have been testing.

Give examples from your collected data to explain your reasons.