Forensic Uses of Deflection (Y) Modulation and X-Ray Dot Mapping

  • Samarendra Basu


The image processing in the scanning electron microscope by deflection (Y) modulation allows augmentation of depths and topographic features of line crossings that naturally occur in many kinds of handwritten documents. A critical evaluation of this method, in comparison with the secondary and the backscattered electron imaging methods, has been made in order to establish that deflection modulation is advantageous for sequencing of intersecting lines of pencils and ball-point pens which leave relatively deep and equal impressions in the paper. The most reliable features of sequencing were less frequent with plastic-point pens. These results have indicated that the sample condition of line crossings is improved by the hardness of the writing tip, by increased writing pressure, and by thick or non-dispersive deposition of ink. The effectiveness of the method is determined by the selected signal (secondary or backscattered), by the accelerating potential of the incident electron beam, and by the specimen-to-electron detector geometry. Knowing these limitations is crucial to successful applications of deflection modulation, since this method is sensitive to the flaws contained in the original signal. The method qualifies for re-examination of the apparently uncharacteristic firing pin impressions of shotguns. The x-ray dot mapping method is well-suited for elemental matching comparisons of multilayered paint chips. Despite the time involved, this method and the backscattered electron imaging method are suitable for examination of fingerprints of magnetic inks.


Line Crossing Incident Electron Beam Gunshot Residue Deflection Modulation Paint Chip 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. 1.
    S. Basu, Forensic uses of deflection (Y) modulation and x-ray dot mapping, in: “Proceedings of the 43rd Annual Meeting of the Electron Microscopy Society of America,” G.W. Bailey, ed., San Francisco Press, Inc., San Francisco, P. 512 (1985).Google Scholar
  2. 2.
    T. Kelly, W.F. Lindquist, and M.D. Muir, Y-modulation: an improved method of revealing surface detail using the scanning electron microscope, Science 165: 283 (1969).CrossRefGoogle Scholar
  3. 3.
    J.C. Russ, X-ray mapping on irregular surfaces, The EDAX Editor 9 (2): 10 (1979).Google Scholar
  4. 4.
    C.A. Grove, G. Judd, and R. Horn, Evaluation of SEM potential in the examination of shotgun and rifle firing pin impressions, J. Forensic Sciences 19 (3): 441 (1974.)Google Scholar
  5. 5.
    T.E. Everhart and R.F.M. Thornley, Wide-band detector for micromicro-ampere-low-energy electron currents, J. Sci Instrum. 37: 246 (1960).CrossRefGoogle Scholar
  6. 6.
    M. Oron and V. Tamir, Development of SEM methods for solving forensic problem encountered in handwritten and printed documents, in: “Scanning Electron Microscopy/1974, Proceedings,” IIT Research Institute, Chicago, Ill., Part I, P. 207 (1974).Google Scholar
  7. 7.
    K.F.J. Heinrich, C. Fiori, and H. Yakowitz, Image-formation technique for scanning electron microscopy and electron probe microanalysis, Science 167: 1129 (1970).CrossRefGoogle Scholar
  8. 8.
    S. Basu, Formation of gunshot residues, J. Forensic Sciences 27 (1): 72 (1982).Google Scholar
  9. 9.
    S. Kimoto and H. Hashimoto, Stereoscopic observation in scanning microscopy using multiple detectors, in: “The Electron Microprobe,” S. Kimoto and H. Hashimoto, eds. John Wiley & Sons, New York,P. 480 (1966).Google Scholar
  10. 10.
    R.D. Koons, Sequencing of intersecting lines by combined lifting process and scanning electron microscopy, Forensic Sci. Internat. 27: 261 (1985).CrossRefGoogle Scholar
  11. 11.
    P. Morin, M. Pitaval, and E. Vicario, Direct observation of insulators with a SEM, J. Phys. E. 9: 1017 (1976).CrossRefGoogle Scholar
  12. 12.
    G.R. Booker, Scanning electron microscopy: The instrument, in: “Modern Diffraction and Imaging Techniques in Material Sciences,” S. Amelinckx, R. Gievers, G. Remaut, and J.F. Landuyt, eds., North-Holland Publ. Co., Amsterdam, P. 553 (1970).Google Scholar
  13. 13.
    N. Niedrig, Physical background of electron backscattering, Scanning 1 (1): 17 (1978).CrossRefGoogle Scholar
  14. 14.
    E.H. Darlington and V.E. Cosslett, Backscattering of 0.5–10 keV electrons from solid targets, J. Phys. D. 5: 1969 (1972).CrossRefGoogle Scholar
  15. 15.
    D.A. Moncrieff and P.R. Barker, Secondary electron emission in the scanning electron microscope, Scanning 1 (3): 195 (1978).CrossRefGoogle Scholar
  16. 16.
    L. Reimer, Scanning electron microscopy-present state and trends, Scanning 1 (1): 3 (1978).CrossRefGoogle Scholar
  17. 17.
    P.A. Waeschle, Examination of line crossings by scanning electron microscopy, J. Forensic Sciences 24 (3): 569 (1979).Google Scholar
  18. 18.
    J. Mathyer, The problem of establishing the sequence of superimposed lines, Internat. Grim. Police Rev., Part I: 238 (1980); Part II: 271 (1981).Google Scholar
  19. 19.
    P.J. Nolan, M. England and C. Davies, The examination of documents by scanning electron microscopy and x-ray spectrometry, Scanning Electron Micros. Part II: 599 (1982).Google Scholar
  20. 20.
    J. Mathyer and R. Pfister, The examination of typewriter correctable carbon film ribbons, Forensic Sci. Internat. 25: 71 (1984).CrossRefGoogle Scholar
  21. 21.
    P.J. Nolan, C. Davies and A.G. Filby, Determination of sequence of writing - a strategy for evaluating new methods, paper presented at the annual meeting of the Intern. Assoc. Forensic Sci., Oxford, 1984; J. Forensic Sci. Soc. 24 (4): 355 (1984).Google Scholar
  22. 22.
    E.J. Korda, H.L. MacDonnell, and J.P. Williams, Forensic applications of the scanning electron microscope, J. Crim. Law Criminol and Police Sci. 61: 453 (1970).Google Scholar
  23. 23.
    J.R. Devaney and L.W. Bradford, Applications of scanning electron microscopy to forensic science at the Jet Propulsion Laboratory, 1969–1970, in: “Scanning Electron Microscopy/1971, Proceedings,” IIT Research Institute, Chicago, ILL. Part II, P. 561 (1971).Google Scholar
  24. 24.
    C.A. Grove, G. Judd and R. Horn, Examination of firing pin impressions by scanning electron microscopy, J. Forensic Sciences 17 (4): 645 (1972).Google Scholar
  25. 25.
    G. Judd, R. Wilson and H. Weiss, A topographical comparison imaging system for SEM applications, in: Scanning ELectron Micros./1973 Proceedings,“ IIT Research Institute, Chicago, ILL., Part I, P. 167 (1973).Google Scholar
  26. 26.
    R. Wilson and G. Judd, The application of scanning electron microscopy and energy dispersive x-ray analysis to the examination of forensic paint samples, in: “Advances in X-ray Microanalysis, L.S. Birks et. al., eds., Plenum, New York Vol. 16, P. 19 (1972).Google Scholar
  27. 27.
    R. Wilson, G. Judd, and S. Ferriss, Characterization of paint fragments by combined topographical and chemical electron optics techniques, J. Forensic Sci 19 (2): 363 (1974).Google Scholar
  28. 28.
    B. Collins, Micro-techniques on the examination of problems in surface coatings, Australian Oil & Colour Chemists ’ Association Proceedings and News 13 (1–2): 6 (1976).Google Scholar
  29. 29.
    P.J. Nolan and R.H. Keeley, Comparison and classification of small paint fragments by x-ray microanalysis, Scanning Electron Micros. Part I; 449 (1979).Google Scholar
  30. 30.
    G.E. Garner, C.R. Fontan and D.W. Hobson, Visualization of fingerprints in the scanning electron microscope, J. Forensic Sci Soc. 15: 281 (1975).CrossRefGoogle Scholar
  31. 31.
    R.D. Olsen, Sr., The chemical composition of palmar sweat, Fingerprint and Identification Magazine 53 (10): 3 (1972).Google Scholar

Copyright information

© Plenum Press, New York 1986

Authors and Affiliations

  • Samarendra Basu
    • 1
  1. 1.New York State Police Crime LaboratoryAlbanyUSA

Personalised recommendations