Problems of Forensic Sciences 2011 Vol. 87 (LXXXVII) 193-203
DETERMINATION OF SEQUENCE OF STROKES THROUGH REFLECTION SPECTRA
Bikram Ashok Vaid, Rajender Singh Rana, Chinki Dhawan
Laboratory of Government Examiner of Questioned Documents, Central Forensic Science Laboratory, Shimla, India
Streszczenie
Nondestructive analysis of two ink strokes in order to determine their sequence still poses a difficult problem for Forensic Document Examiners and at times may lead to inconclusive if not erroneous results. A number of attempts have been made in the past using scanning electron microscopy and optical microscopy to address the problem. In some cases destructive analysis is also suggested, but since the evidentiary value of the exhibit under examination shall cease to exist, such a technique is not advised in actual casework. In this work, the sequence of two intersecting strokes has been determined by studying the reflectance spectra of ink strokes at three different points, viz. one each on two intersecting strokes and the third at the point of their intersection using a video spectral comparator 2000HR (VSC-2000HR). Since reflection is a surface phenomenon, the spectra at the point of intersection will correspond to the subsequently executed stroke provided that the initial stroke had completely dried before the execution of the subsequent stroke. This technique is nondestructive in nature and has been demonstrated to add more objectivity to the determination of the order of two intersecting strokes, which at times poses a problem due to the occurrence of an optical illusion. The authors have experimented with determining the sequence of two heterogeneous strokes (i.e. samples comprised of two different inks) with a number of permutations and combinations.
Słowa kluczowe
Sequence; Reflection spectra; Surface phenomenon intersecting stroke