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a b
Figure 4.9 a) Damaged mobile recovered from blasts, b) Single bit analysis using SPM
Scanning electron microscopes (SEM) play an important role in forensic examinations.
SEM is considered useful for a range of applications and materials due to its extremely
good depth of focus and high to low magnification. SEMs have been used in gunshot
analysis, firearm identification, identification of gemstones and jewellery, examination of
paint particles and fibres, handwriting and print examination, counterfeit bank notes,
trace comparisons, examination of non-conducting materials, and high resolution surface
imaging. In gunshot residue analysis of the specimen stub (cartridge), SEM identifies the
particles due to their high contrast with the stub background. In bullet comparison tests,
bullets fired from the same gun can be identified from marks left as a result of the barrel
of the gun and the firing pin. The high depth of focus of an SEM provides an advantage
over optical microscopy in such examinations, and the backscattered electron detectors
can enhance markings on the bullet while suppressing detection of dust particles. 19 Yang
et al. have conducted an investigation into metallic nanoparticles of gun shot residues
using Electron microscopy. Their study has determined the method by which these
nanoparticles are formed and proposes a model for their synthesis. The additional
information obtained from this synthesis is expected to help in solving crimes through
forensic studies (Yang et al., 2006).
Intel has developed a cantilever based identification method for analysing molecules. This
method has application in identity testing for criminal investigation and forensic studies
(also known as DNA testing). The method is based on the identification of target
molecules (or analyte) using probe molecules (which bind the analyte). The probe or the
analyte is attached to the cantilever, and if it binds to its counterpart then the cantilever
is deflected. A magnetic counterbalancing force is used to balance the cantilever, and
detection is based on the magnitude of the counterbalancing force. The following probe –
analyte combinations have been successfully demonstrated, oligonucleotides-nucleic
acids, and protein/peptides-antibodies (Intel Corp., 2006). Integrated Nano-technologies
have patented a method for detecting a target nucleic acid. In this method,
oligonucleotide probes are integrated in an electrical circuit such that they are not in
contact with each other. This gap is bridged when a complementary target nucleic acid
joins the two probes. This results in a current that can flow through the probes
(Integrated Nanotechnologies, 2002).
4.4 Quantum Cryptography
Cryptography is the art of writing secret codes and is commonly used to send information
from one place to another without third party interference. In modern times,
cryptographic techniques form the central part of information security and related
applications. The most popular and commonly used cryptographic technique is the Public
Key system also known as the RSA encryption (named after mathematicians - Ronald
Rivest, Adi Shamir, and Leonard Adleman). This method is widely used in software
19 Carl Zeiss: http://www.smt.zeiss.com/C1256E4600307C70/EmbedTitelIntern/forensic/$File/forensic.pdf
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