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May 21, 2020 - BY Vaishnavi Hitendra Thakre

Ink Analysis : A versatile approach in questioned document examination

Background

Wherever question over the authenticity of anydocument is raised, the questioned document examiners are called upon.Questioned document is basically a document having authenticity under questionwhich is subjected to a forensic document examination.  The primary purpose of examining the disputeddocuments is to give opinion upon the questions that are raised upon theauthenticity of the document using scientific principles and techniques. Questioneddocuments could involve any type of document for an instance a property will, asuicide note, a blank sheet possessing indentations, bank cheques and manymore. The examination of documents includes detecting alterations andobliterations, analysis of paper, detection and examination of forgery, origin,determining authenticity, and others.

This blog summarizes various techniques utilized inforensic examination of inks as well as the importance of ink analysis so farin the field of investigation.

What is the Role of Forensic QDE (QuestionedDocument Examiner)?

The forensic document examiner plays a crucial roleof uncovering the minute details in the document sample such as in signature orin handwriting. These are the details that cannot be detected or uncovered byan untrained person.

Why ink analysis?

The forensic analysis of ink is a frequentrequirement in casework in order to identify whether the inks on a document ordocuments are same or different. Hence, the document examiners are often calledupon to identify the ink involved and to determine the actual source of the inkon a document. It’s a crucial part of forensic document examination since it isused in both handwritten and printed documents.

The importance of ink analysis has been noted incase of obliterations for differentiating the ink on basis of its chemical composition;further, the source and also the age of ink which ultimately gives the approximateage of the document providing leads and clues in the investigation process. Thereare different types of inks available which are used in different pens such asball pen ink composing of dyes and organic solvents, gel pen, roller ball pen whichuses gel-based inks, fiber or porous tip pen, fountain pens that useswater-based inks etc.

Techniques of Analysis

Non-Destructive: Integrity of the sample havingevidential importance is of fundamental value in forensic examination. Hence,in order to maintain the integrity of documents, the non- destructivetechniques are always preferred over the destructive ones.  

Microscopy

Preliminary examination of ink is performed prior tothe chemical and instrumental analysis. This includes examination of ink by theuse of microscopes and optical sources without detaching the inked portion fromthe document.

Stereomicroscope is used to determine the type ofink, its color or to determine additional marks generated due to pointed tip,blunt tip, damaged writing tip leading to the identification of a class ofwriting instrument. This helps in determining the composition of ink used. Inoptical examination various light sources like UV radiations, IR radiations areused as different inks reflect differently with these light radiations.

Video SpectralAnalysis of Ink

We are aware about the fact that the unaided humaneye can perceive only a certain range of colors of a particular wavelength inthe electromagnetic spectrum. Yet there are other ranges also present such asinfra red and ultra violet range. Although these are invisible but can beconverted to visible using instrumentation. VSC is that one comprehensivedigital system which aids our eyes to perceive these invisible ranges.

Inks are composed of different dyes. These dyes orthe colors can appear similar to our unaided eyes. For example, two bluecolored inks are difficult to be differentiated by visual observation as thecolor is same but the colors could behave differently when perceived under UVor IR range. It’s this behavior that lets the examiner differentiate it. Thespecialized filters of light and the photographic films allow uncovering theminute details of the document sample. These aids show peculiar properties suchas luminescence, transparency, etc. depending upon the chemical properties. Thus,the VSC is one of the reliable instruments used for the questioned documentexamination.

Destructive: 

Techniques incorporating chemical analysis of theink present on the document fall under destructive category since for sampleanalysis the portion of the document containing ink is cut and thus the sampleis destructed.

 Chromatography

Various chromatographic techniques such as TLC, GLC,and HPLC are utilized for the qualitative ink analysis in order to separate thecomponents of ink thereby determining the composition. Most commonly usedtechnique is the TLC (Thin Layer Chromatography) which incorporates the use ofchromatographic plate and the alcohol based solvent for the purpose of inkseparation.   

 Capillaryelectrophoresis

It is similar to HPLC but uses small amount ofsample. Hence, adopted in cases where the sample is limited. Herein, thecapillary is filled with a conductive fluid with designated pH value. Theconductive fluid then serves as the buffer solution in which the sample isseparated.

Infraredspectroscopy

It is used for the characterization of ink. Thedyes, additives and solvent present in the ink show different absorption peakin the spectrum which are unique for every substance and compared with thestandard peaks for identification purpose.

GCMS

GC along with MS i.e. mass spectrometer is one ofthe best techniques used for ink analysis wherein firstly the components areseparated by gas chromatography followed by the identification on the basis ofmass/charge ratio.

In the examination of questioned documents, thenon-destructive techniques are preferred until and unless it is very necessaryto adopt the destructive ones in order to reach to a definite conclusion. 

References

“Alteration/Obliteration & Ink Examinations.”Questioned Documents - Norwitch Document Laboratory, www.questioneddocuments.com/alteration-obliteration-ink-examinations/.

“Ink Analysis.” Forensic Examination Services, www.docexam.co.uk/ink-analysis-41.html.

Teresa. “Introducing The Role Of The HandwritingForensic Document Examiner.” Handwriting Forensics Blog, 9 Sept. 2017,teresadeberry.com/introducing-role-forensic-document-examiner/.

Posted January 16, 2019. “The Role and Importance ofa Forensic Examiner.” Marty Pearce, CDE, 16 Jan. 2019,www.martypearce.com/the-role-and-importance-of-a-forensic-examiner/.