It is 1979. A man walks into a bank, covers his face with a balaclava and hands the only cashier on duty a note and a carrier bag. The note reads: 'I HAVE A GUN. GIVE ME THE MONEY OR I WILL SHOOT YOU'. The terrified cashier thrusts some notes into the carrier bag and hands it to the man. He runs off, just as the cashier manages to activate the alarm.. In his haste to escape, he forgets to ask for the return of his demand note. Two days later, he answers a knock at the door and discovers two police officers, who have come to arrest him for armed robbery. He is so surprised that he confesses on the spot.
A police officer told me a version of these events many years ago. The story may be apocryphal, but it serves to illustrate the major impact of a piece of newly operational forensic equipment, not only in solving cases of armed robbery, but also terrorism, murder, fraud and corruption, for example. The existence of ESDA (ElectroStatic Detection Apparatus) was not widely known amongst the criminal fraternity in its earliest days, but its use in a widely reported case of police corruption ensured that its existence eventually became public knowledge.
So what is ESDA and what does it do?
According to Foster and Freeman, its manufacturers, ESDA is 'the leading technology for detecting indented writing on questioned documents'. When you write on the top sheet of a pad of paper, the writing will leave indented impressions in the sheets underneath. In my armed robbery story, indented impressions of the offender's address were found on the demand note. Just how many sheets will bear impressions depends on the writing implement, the degree of pen pressure and the type of paper. Writing made with a ballpoint pen with reasonably firm pressure on good quality paper may leave indented impressions on up to six underlying sheets. On the majority of these underlying sheets, the impressions are not visible on the paper surface. However, ESDA is such a sensitive technique, that it may be possible to visualise the impressions on all six sheets.
The equipment is very easy to operate. Here is a video of a police officer developing indented impressions in documents from a murder case.
ESDA works by creating an invisible electrostatic image of the indented writing onto the surface of a plastic film. The impressions are visualised by pouring a mixture of glass beads and charge sensitive toner (like you find in photocopiers) over the surface, until the image is developed. A permanent record of the image can be made by covering the surface with a sheet of adhesive transparent plastic. Known as an ESDA 'lift', the resultant transparency consists of the plastic film bearing the visualised indented impressions covered by the adhesive plastic. The lift is trimmed to size and can be used to overlay writing which is suspected of having produced the impressions or simply read for information purposes. If the impressions are of particularly good quality, they can form the basis of a forensic handwriting comparison with a suspect's writing.
A variety of information can be obtained from indented impressions. If a page has been torn out of a diary, ESDA may be able to detect what was removed by examining the pages on either side. In a murder case, where the victim knew her attacker, the victim had made a note in her diary that she would be meeting her attacker on this particular day. Whilst checking that there was nothing to connect him with the crime, the murderer discovered the victim's diary. He tore out the offending page and threw it away. An ESDA examination of the pertinent pages of the victim's diary revealed the attacker's name.
A man committed suicide and left a bitter note for his wife. She has destroyed the note because she feels she drove her husband to take his own life and cannot face his family. Eventually, she tells the police that there was a note and it had been written on the pad by the telephone. An ESDA examination of the top sheet of the pad would show exactly why her husband committed suicide and why she felt so guilty.
A suspect in a case of money laundering passed four handwritten receipts to the police, which, he stated, accounted for four large payments made into his business bank account. The receipts covered a four month period between June and September 2007 and were dated at monthly intervals. The police suspected that the receipts were false and had been created purely to legitimise the transactions. Were the dates on the receipts genuine?
By using ESDA, it was discovered that there were indented impressions of the writing from the receipt dated in September 2007 on the receipts dated in August, July and June 2007. There were also impressions of the August receipt on the July and June receipts and impressions of the July receipt on the June receipt. This is clearly impossible if the receipts are dated correctly. Undoubtedly, all the receipts had been written at one sitting and their dates were not genuine.
I'm sure you could think of many more examples where ESDA would be invaluable in helping to solve crimes.
A big bonus of the ESDA technique is that the document containing the impressions is not damaged in any way, Furthermore, provided that the document has not been treated with fingerprint reagents, the technique still works after many years, and could, therefore, be of value in cold cases.
So when your characters decide to send a handwritten anonymous letter or plan an armed robbery on paper, they should take care what they leave behind!
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