To Study the Effect of Source Media on the Enlargement and Reduction of Faxed Documents
Komal Saini and Mansi Gupta*
Department of Forensic Science, Punjabi University Patiala, India
Submission: June 01, 2018;Published: June 14, 2018
*Corresponding author: Mansi Gupta, Department of Forensic Science, Punjabi University Patiala, India, Email: mansigupta103@gmail.com
How to cite this article: Komal Saini, Mansi Gupta. To Study the Effect of Source Media on the Enlargement and Reduction of Faxed Documents. J Forensic Sci & Criminal Inves 2018; 9(3): 555764. DOI:10.19080/JFSCI.2018.09.555764.
Abstract
To analyze whether the print media can be linked to the documents faxed through it, laser and inkjet printouts were used as the source documents. Totally, eighty seven fax machines were used, among which two were chosen as senders and eighty five as receivers. The faxed documents were analyzed vis –a – vis the source printed documents. Results revealed that the nature of the print media of the source document affected the dimensional changes (enlargement as well as reduction) occurring in the vertical and horizontal dimensions of the text.
Keywords: Forensic Science; Questioned Documents; Fax Documents; Horizontal; Vertical Dimensions; Statistical Analysis
Introduction
In many fax document examination cases, ideal condition exists for the complete and comprehensive examination of documents [1]. This includes the knowledge about the sending and the receiving machines, availability of contemporary specimen and original faxed documents as fax machines are used to send important business and other documents to distant places, questioned document examiners are generally asked to answer queries related to authenticity of source and date of faxed documents. There is also condition where the original print document may not be available for examination. The current study has been conducted in order to determine that if the original printout specimen (laser and inkjet printout) and the faxed documents are available, is it possible to link the fax document to the original printout or not. This may be helpful in cases where multi page documents are available and dispute of substitution might be there [2].
Materials and Methods
Sample Collection
Two standard documents, produced on A4 paper at 600 dpi were generated by using a laser printer and an inkjet printer and these were used as the source documents in the study. These documents were prepared using Microsoft Word with the font style set as ‘Times New Roman’, font size as 12 and line spacing as 2. These documents were then faxed across eighty seven fax machines selected for this research project. Two fax machines were used to send or transmit the source documents [3]. These machines were used only for the purpose of scanning and transmitting the document. The remaining eighty five machines received the transmitted documents. Thirty receiving fax machines comprised laser printers, twenty five had inkjet printers and the remaining thirty had thermal printers. The source documents were faxed in standard resolution from the two sender fax machines to the eighty five receiver fax machines producing 340 (2 × 85 = 170; 170 × 2 = 340; (Figure 1) samples. To ascertain the changes between the original printouts and faxed documents, the text of the fax document was measured in both the vertical and horizontal dimensions.
![Click here to view Large Figure 1](images/JFSCI.MS.ID.555764.G001.png)
Vertical dimensions
a. Changes in the distance between the baseline of the heading and the baseline of the first line were denoted as “a” (Figure 2).
![Click here to view Large Figure 2](images/JFSCI.MS.ID.555764.G002.png)
b. Changes in the distance between the baseline of the heading and the baseline of the last line were denoted as “b” (Figure 2).
c. Changes in the distance between the first and last lines of text were denoted as “c” (Figure 2).
d. Changes in the distance between each successive line of text were denoted as “d1 - d13” (Figure 2).
e. Changes in the distance between the borders on both sides of the document, starting from the outside to the inside, were denoted as “V1, V2 and V3” (Figure 2).
f. Changes in the height of the text in each line were denoted as “e” (Figure 2).
Horizontal dimensions
a. Changes in the length of the lines were denoted as “3a- 3n” (Figure 2).
b. Changes in the distance between the borders on both sides of the document, starting from the outside to the inside, were denoted as “H1, H2 and H3” (Figure 2). Measurement of the dimensions of the text; (a) shows distance between the baseline of the heading to the baseline to the first line shows distance between the baseline of the heading to the baseline to the last line; shows distance between the baseline of the first line to the baseline of the last line, shows measurement of the height of the text in each line, (d1–d13) shows measurement of the line spacing; (V1, V2 and V3) measurements of the distance between the borders on both sides in the document starting from outside to inside, (3a-3n) shows measurement of the individual horizontal lines; (H1, H2 and H3) shows measurements of distance between the borders on both sides in the document starting from outside to inside.
Analysis
Qualitative Analysis
Measurements of the dimensions of faxed documents and original documents (laser and inkjet printout) were compared. The original laser and inkjet printouts were also examined to determine whether any differences existed in the dimensions. The observations and calculation were done according to Welch (1998) and Lindblom et al. [4].
Statistical Analysis
All measured distances are expressed in centimetres (±0.05) and the values were entered into the SPSS (Statistical Package for Social Sciences) (version 19.0) [5]. software for the application of statistical tools. Stepwise Discriminate Analysis method was used as the statistical tool to identify the important variables discriminating the faxed samples between the laser and inkjet printout groups. Discriminate function analysis was used to determine the variables that differed between two or more naturally occurring groups [5]. The discriminate score equation is as follows- D = a+W1X1 + W2X2 + W3X3 = …………+ WiXi where
D = discriminate function
W1,, W2... Wi = the discriminant coefficient or weight for that variable
X1, X2...Xi = respondent’s score for that variable
a = constant
Results and Discussion
Qualitative Analysis
Analysis was performed by calculating the percentage of the range of enlargement and reduction in dimensions for all the variables. The results have been shown in (Table 1). Compared with the original document, the faxed documents exhibited enlargement as well as reduction along both the vertical and horizontal dimensions. Furthermore, the range of reduction was greater when inkjet printouts were used as the print media. By contrast, the percentage of enlargement was greater when the source document was a laser printout.
![Click here to view Large Table 1](images/JFSCI.MS.ID.555764.T001.png)
Result for Statistical Analysis
Stepwise Discriminate Function [6-8]. Analysis was applied as a statistical tool for the data collected in this study. All the variables were tested for determining the group memberships. The results showed considerable possibility of determining whether the fax was sent from a laser or an inkjet print media. The variables that were most significant for the classification of facsimile samples between the laser and inkjet printout groups have been given in (Table 2). The chi - square test statistic was 0.00 (statistically significant) (Table 3). Shows the unstandardized coefficients of these variables. These coefficients along with the variable measurement values have been substituted in equation 1 and then the discriminate score has been calculated.
(D = a+W1X1 + W2X2 + W3X3 = …………+ WiXi ) equation (1)
![Click here to view Large Table 2](images/JFSCI.MS.ID.555764.T002.png)
At each step, the variable that minimizes the overall Wilks’ Lambda is entered.
a. Maximum number of steps is 100.
b. Minimum partial F to enter is 3.84.
c. Maximum partial F to remove is 2.71.
d. F level, tolerance, or VIN insufficient for further computation.
![Click here to view Large Table 3](images/JFSCI.MS.ID.555764.T003.png)
Each sample’s discriminate score could be computed by entering its variable values into the equation. The values of the constant and the discriminate coefficients (W1, W2…Wi) could be obtained from Table 3. Then, the values of the predictor variable (X1, X2… Xi) Could be measured from a sample and entered into the equation. A discriminate score could be calculated from this equation and compared with the group cancroids given in Table 4. If the discriminate score was close to 0.828, then the print media of the source document for the fax samples might be laser printout. Similarly, if the discriminate score was close to -0.808, then the print media of the source document for the fax sample could be inkjet printout. The closer the discriminate score was to the group centric values, the more accurately group could be determined. This helps in the classification of any random fax document whose origin might be unknown.
![Click here to view Large Table 4](images/JFSCI.MS.ID.555764.T004.png)
The document examiner can take measurements of the fax document and input the values into this formula to identify which group the sample might belong to. The final classification result of the study is shown in Table 5. In total, 80.4% of the fax samples were correctly classified into the laser or inkjet printout group. The second times, 79.8% of the samples were classified correctly in cross validation. This indicates a high probability that the document examiner will be able to differentiate and determine the print media source of the original document by following this procedure. Lindblom et.al [4]. stated that the receiving fax machine contributed more to output size than did the transmitting machines; however, the behaviour of the fax machine could be unpredictable. The present study concluded that dimensional variables could be used to classify samples into the laser and inkjet original printout groups. Thus, the fax samples generated from laser and inkjet print media sources could be successfully differentiated and this aspect was not considered in earlier studies.
![Click here to view Large Table 5](images/JFSCI.MS.ID.555764.T005.png)
a. 80.4% of original grouped cases correctly classified.
b. Cross validation is done only for those cases in the analysis. In cross validation, each case is classified by the functions derived from all cases other than that case.
c. 79.8% of cross-validated grouped cases correctly classified.
Summary and Conclusion
The present study analyzed whether the print media of the source document could be linked to the faxed document generated from it. For this purpose laser and inkjet printouts were faxed using various fax machines. Two facsimile machines were chosen as senders and eighty five machines received the fax. Among the eighty five facsimile machines, thirty were attached to laser printers, twenty five to inkjet printers and thirty to thermal printers. Qualitative analysis revealed that the range of reduction in the fax samples was greater when the print media was an inkjet printout and the range of enlargement was greater when the source media was a laser printout. Stepwise discriminate function analysis was conducted to classify the fax samples on the basis of the print media of the source. Significant variables were found to be V1, d12, d11, 3n, 3c, H3, H1, 3g, 3e and 3c among the fax samples. These variables were an important contributing factor for the classification. The classification results showed that 80.4% of the original groups were correctly classified and 79.8% of the cross-validated groups were correctly classified. Accordingly, when a faxed document is received by a questioned document examiner, differentiating between samples generated from a laser print media source and those generated from an inkjet print media source might be possible.
Acknowledgement
A sincere thank you to HOD, other faculties and other staff from Department of Forensic Science Punjabi University Patiala for providing platform to conduct this study. Also sincere thank you to UGC-for providing me scholarship to cover the expenses that ocured while doing the study.
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