الفهرس 
IntroductionOnly 14 pages are availabe for public view
Abstract
Documents are any material containing marks, symbols or signs that convey meaning or message to someone. Therefore, changing, deleting, or adding information on it or replacing an entire page with a counterfeited page is considered forgery.
Within the last years, forgery has markedly increased and expanded to encompass computers and printers’ usage that facilitated the production of fraudulent printed documents by even non-experts.
Printers and photocopiers leave their imprints on the produced documents. Examination of the printed output in a questioned document is essential as it provides information about the producing device, it can provide important information about document’s authenticity and genuineness. Identification of a document source plays an important role to confirm the authenticity of the printed document. It is also required in providing clues and leads in several criminal cases and in pinpointing the source of leakage of secure documents, counterfeiting and forgery.
This study aims to compare the characteristics of different computer printed documents to identify the type of the producing output devices [(photocopier (PC), inkjet (IJ), and laser printers (L)].
Methodology:
This study is a comparative cross-sectional study conducted at Forensic Medicine and Clinical Toxicology Department, Faculty of Medicine, Ain Shams University.
Materials used:
Printing medium: white blank paper (80 GSM, Allam Premium, size A4, 210 X 297mm).
Computer-typed documents were typed using the same computer model.
Hand-written samples were written using the same pen (black rollerball pen), then they were scanned using the same scanner model.
Signed documents were signed using two types of pens (blue rollerball pen and blue ballpoint pen).
Different models of inkjet, laser printers and photocopiers were used (four models of each).
All printed documents were examined with:
- Paper Thickness Measuring Device, Mitutoyo 7360 Dial Thickness 0-10mm, Japan.
- USB Powered 50-500X Digital Microscope, China.
- Ultraviolet (UV) lamp 365 Mila T5 Electronic Fixture, China.
Samples:
A total of 384 paper documents were divided into three groups (A), (B) and (C):
group (A):
• 132 computer-typed sample documents were typed on Arabic language. Font used is ”Black Simplified Arabic”, size ”16”.
• The samples were subdivided into 3 subgroups: Subgroup A(IJ), A(L) and A(PC): 44 samples were collected from every group, 11 samples were collected from each of the chosen models.
• The printed markings were examined and compared with that produced by their same group or other groups.
group (B):
• 132 hand-written sample documents were written, scanned and then printed by the same selected devices as in group (A).
• The samples were subdivided into 3 subgroups: Subgroup B(IJ), B(L) and B(PC): 44 samples were collected from every group, 11 samples were collected from each of the chosen printers’ models.
• The printed markings were examined in the same way like in Computer-typed documents.
group (C):
• 120 Signed documents were subdivided into 4 subgroups: Subgroup C(I), C(II), C(III) and C(IV): 30 samples were collected from every group.
• Documents of group C(I) were pre-signed using the selected ballpoint pen then computer-typed after 3 hours interval. While documents of group C(II) were computer-typed then signed after 3 hours interval using the same pen.
• Documents of group C(III) were pre-signed using the selected rollerball pen then computer-typed after 3 hours interval. While documents of group C(IV) were computer-typed then signed after 3 hours interval using the same pen.
• The 30 documents of every group were produced from three randomly selected devices; an inkjet, a laser printer and a photocopier as ten samples from each device.
Documents examination:
• Examination of groups (A) and (B):
1) Documents were examined by the Paper Thickness Measuring Device to get the mean thickness of letters as follows:
(i) Measuring the thickness of the studied document at 4 unprinted areas, and 4 printed areas then their mean thickness (in µm) was calculated.
(ii) Difference between the mean thickness of printed and unprinted areas was calculated to get the mean thickness of letters (in µm).
2) Documents and printed markings were magnified and examined by digital microscope and ultraviolet rays to compare between their characteristic features: brightness, homogeneity, and edges of the printed markings. Scattering of ink or toner, effect of folding and scratching of the paper over the printed markings.
• Examination of group (C):
1- Documents were examined by the Paper Thickness Measuring Device to get the mean thickness at the intersecting site between signature and typing as follows:
i. Measuring the thickness of the studied document at 3 unprinted areas, 3 printed areas and 3 printed areas where signatures intersecting typing then their mean thickness (in µm) was calculated.
ii. Difference between the mean thickness of unprinted areas and sites of intersection was calculated to get the mean thickness of the intersecting sites (in µm).
2- Documents and intersecting sites were magnified and examined by digital microscope and ultraviolet rays to compare between their characteristic features: color of intersecting sites, homogeneity of printed markings and signature’s stroke, effect of paper folding and scratching at the intersecting sites and presence of ink or toner over them.
Statistical analysis:
The data was collected, tabulated, and statistically analyzed.
Ethical consideration:
This study was conducted after getting approval of the ethical committee of Faculty of Medicine, Ain Shams University, code number (FWA000017585).
Results:
This study adopted the optical examination using direct light digital microscope and ultraviolet light to extract the characteristic features of printed documents produced by each class of the printing devices.
The study showed that the printed documents produced by different models of the same type of printer devices either (inkjet, laser or photocopier) displayed no significant difference as regards the following studied characteristic criteria: brightness of printed markings, their homogeneity, their edges, scattering of ink or toner either around the printed markings or over the plain paper, the effect of folding and scratching the paper over different printed markings and lastly measuring and calculating the mean thickness of letters.
As regards documents of group (A): inkjet-printed markings were dull, not homogenous, and their edges were hairy-like and ill-defined. While, laser-printed markings were bright, homogenous, and their edges were sharp and well defined. At the same time photocopied markings were moderately bright, moderately homogenous, and their edges were slightly sharp. As regards scattering of ink or toner, it was absent on the paper but present around the inkjet-printed markings; but it was present only on the front of paper documents and absent around laser-printed markings. Toner was present on both the front and the back of the paper documents but absent around photocopied markings. Furthermore, folding and scratching had no effect on inkjet-printed markings; on contrary to printed markings in documents produced by laser printers and photocopiers which were broken, removed, and disrupted by folding and scratching. Comparing the mean thickness of letters in computer-typed documents shows significant difference between printed and unprinted areas.
As regards documents of group (B): The inkjet-printed markings in hand-written and scanned documents were dull, not homogenous, and their edges were hairy-like and ill-defined. On the other hand, laser-printed markings in hand-written and scanned documents were bright and moderately homogenous, and their edges were irregular. Photocopied markings in hand-written and scanned documents were moderately bright and moderately homogenous, and their edges were festooned. As regards scattering of ink or toner; it was absent on the paper but present around the inkjet-printed markings. Toner was also present on the front of the paper documents as well as around laser-printed markings. At the same time toner scattering was present on both the front, the back, and around photocopied markings. Folding and scratching had no effect on inkjet-printed marking, conversely to printed marking in documents of laser printers and photocopiers which were broken, removed, and disrupted by folding and scratching papers for several time. Comparing the mean thickness of letters in hand-written and scanned documents shows significant difference.
As regards documents of group (C):
Examining the intersecting sites in documents of groups C(I) and C(II) produced by the same inkjet printer shows black discoloration with blue dots in documents of group C(I) and red discoloration in documents of group C(II). Both groups showed: i) Scattered ink at the edges between the signatures’ strokes and the inkjet-printed markings. ii) No homogeneity of printed markings and signed strokes. iii) Folding and scratching of papers at the sites of intersection had no effect. iv) Significant difference between mean thickness of the intersecting sites in the compared groups.
On the other hand, the intersecting sites in documents of groups C(I) and C(II) produced by the same laser printer shows black discoloration in documents of group C(I) and orange discoloration in documents of group C(II). Both groups showed: i) Toner scattered next to the printed marking. ii) Printed markings appeared homogenous, while signatures’ strokes displayed no-homogeneity. iii) Folding and scratching of paper at the site of intersection induced breaking, removal and disruption of printed marking leaving blue background in documents of group C(I) and white background in documents of group C(II). iv) Non-significant difference between the mean thickness of the intersecting sites in documents of the two compared groups.
The intersecting sites in documents of groups C(I) and C(II) produced by the same photocopier shows black discoloration with blue dots in documents of group C(I) and orange discoloration in documents of group C(II). Both groups showed: i) Toner scattered next to the photocopied marking seen by UV rays. Furthermore, ii) The photocopied marking appeared moderately homogenous, opposing to the signatures’ strokes which appeared not homogenous in documents of the two compared groups. iii) Folding and scratching of paper at the site of intersection induced breaking, removal and disruption of photocopied marking leaving blue background in documents of group C(I) and white background in documents of group C(II). iv) Non-significant difference between the mean thickness of the intersecting sites in documents of the two compared groups.
Examining the intersecting sites in documents of groups C(III) and C(IV) produced by the same inkjet printer shows black discoloration with blue dots in documents of group C(III) and red discoloration in documents of group C(IV). Both groups showed: i) Scattered ink on the signature could not be detected in documents of both groups. ii) no homogeneity of printed markings, while signatures’ strokes were moderately homogenous. iii) Folding and scratching of paper at the site of intersection had no effect. iv) Non-significant difference between the mean thickness of the intersecting sites in documents of the two compared groups.
Examining the intersecting sites in documents of groups C(III) and C(IV) produced by the same laser printer shows black discoloration in documents of group C(III) and red discoloration in documents of group C(IV). Both groups showed: i) Scattered toner on the signature could not be detected. ii) The printed markings appeared homogenous, on contrast to signatures’ strokes which appeared moderately homogenous. iii) Folding and scratching of paper at the site of intersection induced breaking, removal and disruption of printed markings leaving a blue background in documents of group C(III) and a white one in documents of group C(IV). iv) Non-significant difference between the mean thickness of the intersecting sites in documents of the two compared groups.
Examining the intersecting sites in documents of groups C(III) and C(IV) produced by the same photocopier shows black discoloration with blue dots in documents of group C(III) and red discoloration in documents of group C(IV). Both groups showed: i) No detected toner on the signatures’ strokes. ii) The photocopied markings and signed strokes showed moderate homogeneity. iii) Folding and scratching of paper at the site of intersection induced breaking, removal and disruption of photocopied markings leaving blue background in documents of group C(III) and white background in documents of group C(IV). iv) Non-significant difference between the mean thickness of the intersecting sites in documents of the two compared groups.