The examination of photocopy documents

Totty, R.N.

doi:10.1016/0379-0738(90)90148-r

Cited by 20 publications

(12 citation statements)

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“…The emergence and widespread use of photocopiers and computer printers during the last two decades has complicated the investigative process [2]. Laser printers have blurred the line between printed and copied documents, necessitating a shift away from the traditional methods used for the analysis of typewritten documents [3].…”

Section: Introductionmentioning

confidence: 99%

Forensic discrimination of photocopy and printer toners I. The development of an infrared spectral library

Merrill

Bartick

Taylor³

2003

Analytical and Bioanalytical Chemistry

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Microscopical reflection-absorption by infrared spectroscopy (R-A IR) was shown as a viable technique for analyzing the polymer resins contained in dry, black photocopy and printer toners. The sampling technique involves a heat transfer of the toner from a document to the reflective surface of aluminum foil followed by analysis by R-A IR. The technique is simple, fast, and readily available to most forensic laboratories. A searchable spectral library was created that contains 807 toner samples analyzed by R-A IR. Ninety-eight groups were established based on spectral characteristics, and a flowchart was developed to assist with group assignments. A blind study was conducted to compare twenty photocopied documents each paired to a test document to determine if the pair could have been produced from the same copier. The analyst obtained 100% correct results in this study. Tests on thirty samples with the spectral library produced 90% first hits for the correct group. The three remaining samples were correctly determined by visual comparison of spectra for the top three hits. An actual case study was conducted where the investigation was narrowed from 400 possible machines to eight based on a comparative study of the photocopy toners.

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Section: Introductionmentioning

confidence: 99%

Forensic discrimination of photocopy and printer toners I. The development of an infrared spectral library

Merrill

Bartick

Taylor³

2003

Analytical and Bioanalytical Chemistry

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“…As a result, photocopying documents has become simple, fast, and inexpensive. A major disadvantage of photocopy machines is that they are now more accessible for illegal activities such as counterfeiting, fraud, false documents, anonymous letters, confidential materials, and acts of terrorism [1,2,3]. Identification of the source of photocopied documents is not an easy task for forensic examiners since chemical and physical characteristics are very similar and numerous manufacturers of photocopy instruments and toner cartridges exist.…”

Section: Introductionmentioning

confidence: 99%

“…Totty [4] reviewed analytical techniques that have been used to characterize toners: visual examination, optical microscopy, scanning electron microscopy (SEM), magnetic viewers, infrared spectroscopy (IR), pyrolysis gas chromatography and/or mass spectrometry (Py-GC, Py-GC/MS, Py-MS), and differential scanning calorimetry (DSC). Early work by Kemp and Totty [5] found that 79 toners from various models of photocopier machines could be separated into 10 groups based on their IR spectra.…”

Section: Introductionmentioning

confidence: 99%

Forensic discrimination of photocopy and printer toners II. Discriminant analysis applied to infrared reflection-absorption spectroscopy

Egan

Morgan

Bartick

et al. 2003

Analytical and Bioanalytical Chemistry

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Copy toner samples were analyzed using reflection-absorption infrared microscopy (R-A IR). The grouping of copy toners into distinguishable classes achieved by visual comparison and computer-assisted spectral matching was compared to that achieved by multivariate discriminant analysis. For a data set containing spectra of 430 copy toners, 90% (388/430) of the spectra were initially correctly grouped into the classifications previously established by spectral matching. Three groups of samples that did not classify well contained too few samples to allow reliable classification. Samples from two other pairs of groups were similar and often misclassified. Closer examination of spectra from these groups revealed discriminating features that could be used in separate discriminant analyses to improve classification. For one pair of groups, the classification accuracy improved to 91% (81/89) and 97% (28/29), for the two groups, respectively. The other pair of groups were completely distinguishable from one another. With these additional tests, multivariate discriminant analysis correctly classified 96% of the 430 R-A IR toner spectra into the toner groups found previously by spectral matching.

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“…Use of photocopying machines and laser printers has increased dramatically over the last 20 years [1,2,3]. Because of the speed, simplicity, and accessibility of photocopying, forensic examiners are now encountering photocopies as questioned documents with increasing frequency.…”

Section: Introductionmentioning

confidence: 99%

Forensic discrimination of photocopy and printer toners. III. Multivariate statistics applied to scanning electron microscopy and pyrolysis gas chromatography/mass spectrometry

et al. 2003

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Copy toner samples were analyzed using scanning electron microscopy with X-ray dispersive analysis (SEM-EDX) and pyrolysis gas chromatography/mass spectrometry (Py-GC/MS). Principal component and cluster analysis of SEM data for 166 copy toner samples established 13 statistically different subgroups, with the presence or absence of a ferrite base being a major division. When toners were compared for which both SEM and reflection-absorption infrared spectral data were available, 41% of the samples could be assigned to specific manufacturers. Py-GC/MS on poly(styrene:acrylate)-based toners produced eight peaks relevant to toner differentiation. One third of the toners clustered in a small group that contained five statistically different subgroups. Of the 57 toners for which both Py-GC/MS and SEM data were available, 31 could be differentiated using the combined analytical results. The synergy of the complementary information provided by Py-GC/MS and SEM narrows matching possibilities for forensic investigations involving copied or laser printed documents.

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The examination of photocopy documents

Cited by 20 publications

References 0 publications

Forensic discrimination of photocopy and printer toners I. The development of an infrared spectral library

Forensic discrimination of photocopy and printer toners I. The development of an infrared spectral library

Forensic discrimination of photocopy and printer toners II. Discriminant analysis applied to infrared reflection-absorption spectroscopy

Forensic discrimination of photocopy and printer toners. III. Multivariate statistics applied to scanning electron microscopy and pyrolysis gas chromatography/mass spectrometry

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