**3.5 Finger print**

In most the crime, fingerprints are the most common type of evidence found on to the crime scene. A fingerprints are impression of friction ridges on human finger. The discovery, visualization of latent fingerprints constitutes an important part of any crime investigation. Finger prints consist of exogenous and endogenous compounds. The endogenous part mainly includes the skin remnants, sweat gland and sebaceous secretions along with many different inorganic and organic substances. The finger prints remains unchanged throughout the life of an individual hence they play very important role in person identification. Usually visible and latent fingerprints are found at the crime scene. The visible prints do not require any aid to be visualized while the latent prints are invisible thus require physical, chemical and instrumental techniques to be visualized [44]. Very few researchers have tried to explore the use of AFM in fingerprint investigation.

Atomic force microscopy technique highlight its use to study the deposition characteristics and detection efficiency of fingerprint details. Direct application of the AFM is not soon in the examination of comparison of the fingerprint but the use of AFM is shown in the fingerprint cases by some researchers. Jones et al. used AFM to characterize the various substrates erstwhile of fingermark deposition in relation to the surface roughness, maximum height variation, skew and kurtosis. The finger prints were developed using iron oxide powder on formica, polyethylene and unplasticised polyvinylchloride surfaces [45]. As per Goddard et al. the limitation of the AFM height imaging to study the fingerprint ridge is the surface roughness when it is in the same order of magnitude as the height of the ridges as shown in **Figure 8** [46]. The same problem avail with lifted finger prints as well as the prints present on the metal surfaces. The roughness of the surface on which the finger prints are present is main obstacle for routine applications of AFM in fingerprint analyses. In case were the surface roughness can be reduced atomic force microscopy can be useful in recovering

**Figure 7.** *The separated epitheca and hypotheca of one cell [43].*

*Atomic Force Microscope in Forensic Examination DOI: http://dx.doi.org/10.5772/intechopen.104704*

the missing details that are essential to reconstruct a fingerprint. This problem was overcome by using scanning Kelvin probe force microscopy performed by Williams and McMurray. They studied the fingerprints deposited on metallic surfaces. They were able to retrieve sufficient ridge detail of fingerprint which were physically removed. Furthermore they demonstrated the use of Volta potential mapping to examine the fingerprint present on planar brass substrates [47].

#### **3.6 Gunshot residues**

Gunshot residues (GSR) mainly contains unburned or partially burnt propellant powder, particles from the ammunition primer, grease, smoke, metal residues and lubricants from the fired cartridge while the organic compounds in GSR originate from propellant and firearm lubricants [48, 49]. The analysis of the inorganic GSR can evidence to be useful in forensic reconstruction of shooting incidents. Techniques such as neutron activation analysis, ICP, atomic absorption spectrometry (AAS), and SEM combined to energy dispersion analysis are used for inorganic GSR analysis [50–53]. Neutron activation analysis are used for analysis of barium and antimony and for lead analysis conventional AAS and ICP are useful. High-resolution ICP-MS are reported to identify lead, barium and bismuth concentrations upto 1 ng/mL [54]. SEM-EDX is considered as golden standard of forensic GSR analysis as it has the ability to characterize GSR both chemically and morphologically. The SEM analysis is a time-consuming process. The organic GSR analysis are done by using gas chromatography, HPLC or GS-MS [55]. For both inorganic and organic GSR characterization time of-flight secondary ion mass spectrometry, Raman micro-spectroscopy and ablation-ICP/MS are reported [56, 57]. Apart from these, AFM technique have shown a great applicability in forensic GSR analysis on the basis of its morphological structure in relation to solving the crime [58].

The estimation of shooting distance plays a vital role in firearm cases also when combined with other evidence it helps in reconstructing shooting events. The bullet entrance hole appearance and the GSR patterns around the wound are usually used

to estimate the firing distance [59–61]. Most commonly used color test Griess test along with series of modified and improved Griess tests are used to determine the presence of nitrites and hence for estimation of muzzle to target distance. Mou et al. reported the application of atomic force microscopy and Fourier transform infrared attenuated total reflectance spectroscopy. They use the techniques for firing distance estimation or muzzle-to-target shooting distance as well as the manufacturers of the cartridge and its powder. In their work, standard procedures contain test firing at various distances along with the evidence pattern comparison. They observed that for the samples the Winchester SuperX and CCI cartridges GSR particle sizes increased as the shooting distance decreased. From the AFM images of GSR they found that particles size distribution is inversely proportional to the shooting distance. AFM can be applied for the investigation of various materials unrelatedly to their conductivity. AFM is a non-destructive technique which helps in measurements in either air, liquid, or controlled atmospheres thus allowing the intact sample to be characterized without any pretreatments of the samples. The AFM images of GSR particles showed with different shapes like spherical, twins-like, irregular, boomerang-like, non-spherical, heart-like, rod-like and cube/rectangular-like as shown in **Figure 9**. The results indicated that the particles size distribution was inversely proportional to the shooting distance [62]. As per Jones when AFM is used for the GSR particles analysis the powder get stuck on the probe tip, thus drastically changing the shape and size of the powder particles resulting into the newer shape formation hence significantly alters the subsequent analysis [63]. This could be considered as a drawback of AFM for the analysis of fine GSR particles. But these same was overcome by Mou et al. which prove to be useful in firing distances determination.

D'Uffizi et al. in their work examine the GSR particles deposited on the bullet and on the shooter hands using combination of scanning electron microscopy + energydispersive spectroscopy, atomic force microscopy and selected-area X-ray photoelectron spectroscopy. The GSR samples were collected using double-sided tape. They studied the micromechanical and micromorphological features of gunshot residue particles. Of importance in this investigation the use of AFM itself (Nanoscope IIIa Digital Instruments microscope, tapping mode, frequency: 250–390 kHz) was done to examine the height and phase imaging [64]. Some research has shown the applicability of AFM in context to forensic gunshot and explosive investigation with regards to physicochemical characterization that can be detected on hairs and in between the ridges of fingermarks.

The mechanical properties of the organic and inorganic particles present in GSR and explosives, were studied by Xu et al. They showed the application of AFM techniques, including force volume mode, phase imaging as well as Kelvin probe force microscopy with resonance enhancement for dielectric property mapping was used to map the local physical properties of mock explosive materials. These work will allow the identification of sub-micrometer heterogeneities in relation to their electrical and mechanical properties [65].

#### **3.7 Explosion**

One of the recent advancements showed the use of AFM as a characterization technique for explosives detection. The surface morphology of explosives such as triamino-trinitro-benzene, plastic-bonded explosives, ammonium perchlorate was analyzed through AFM [66–68]. The surface morphology of such explosives helps in understanding the different characteristics of explosives which can help in identification [69].

*Atomic Force Microscope in Forensic Examination DOI: http://dx.doi.org/10.5772/intechopen.104704*

#### **Figure 9.**

*AFM images of GSR particles showing various particle shapes, twins-like (a), heart-like (b), boomerang-like (c), and rod and cube like (d). The bullet type is CCI and the shooting distance is 10 ft.*

Accumulation of explosives namely 2,4,6-trinitrotoluene (TNT) and triacetone triperoxide (TATP) in chemically treated hair sample was studied by Oxley et al. [70] using AFM and SEM. The interaction of TNT and TATP as a function of chemical pretreatment with acetonitrile, neutral and alkaline hydrogen peroxide, methanolic potassium hydroxide and potassium permanganate was studied and further the morphological changes which resulted from these treatments were studied. Hair examination surface showed different degrees of smoothening. Density functional theory calculations were employed to known the possible nucleation sites of TATP microcrystals on the hair samples. From their calculations study they concluded that the dark hair adsorbs explosives better than light hair. The authors have showed the use of AFM on their previously described applications of AFM in hair structure investigations [17, 36, 71]. Studied reported shows that AFM play a vital role in trace evidence analysis in post-explosion cases. These studies indicate that recently the potential of the AFM technology has been explored in relation to the forensic evidences analysis and the full potential of technology is yet to be discovered. The possibility of mapping a number of physical and chemical material properties prove to be a worthy contribution in distinguishing the different components in complex heterogeneous structure of explosive residues samples. The AFM technology is only a complementary technique its use can be enhanced if combined with other analytical technique which can prove to be of great importance in forensic context for not only examination of GSR or post explosives residues but also for other trace evidences found on to the crime scene.

Valle et al. [72] used AFM to investigate and identify several characteristics of firearms. Replica molding of the head of these cases was done using the fired cartridge cases and the surface morphology of replicated areas at the breech faces were studied. In this framework, the method showed reproducibility of different copies of the similar sample indicating that they are indistinguishable over all the accessible length scales.

Researchers have also shown the utility of AFM in fire investigation cases. In fire cases the determination of source of fires plays very important role in order to validate [73, 74]. In fire cases, molten electric marks are found on the electric arc bead. Examination of these marks can help to determine the source of the fire. Gao et al. used OM and AFM to examine a molten mark on copper wire by artificially creating the molten mark inflicted on the wire under laboratory conditions. The AFM results showed that the technique is an brilliant add-on to examine the copper molten mark and thus provide excellent data to confirm the actual causes of fire [75].

#### **3.8 Soil sample analysis**

Soils vary among different areas and possess characteristics due to their natural effects and transfers made by human being and other living beings with time. Examination of soil in forensic context can help in determination of crime location. Investigative and interpreting the soil or sediment can help in their origin determination [76]. Konopinski et al. studied the grain surface texture of quartz sand using AFM. AFM analysis provide topographical data from the grain surface that permits statistical analysis, 3D reconstruction and quantitative valuations of the microscopic surface textures. AFM offers numerous statistical methods which can discriminate between grain surface textures and also helps in creating automated database to compile and generate reports. AFM has great potential to be used for forensic analysis where sample preservation is extremely valuable. As per Konopinski et al. using AFM helps in quantifiable measurement of quartz grain surface textures which opens up a number of possibilities for forensic quartz grain surface texture analysis as it provides a corroborative independent verification of quartz type classifications as shown in **Figure 10** [14].

Sullivan et al. in their work investigated the surface characteristics of plastic wrapping materials of forensic interest in soil environments in order to determine the environmental factors that influence the degradation process of such polymers. They buried polyethylene bags and poly (vinyl chloride) sheeting in model environments surrounding different soil types, moisture content, pH and temperature. Atomic force microscopy was used to study the changes which results on the polymer surface at a nanometre level. They found that over a 2-year burial period, the degradation of polyethylene was greater by an increased moisture content and a raised soil pH. The plasticizer content of poly (vinyl chloride) was got affected by burial, thus leaching of the same was observed in all environments continually over the burial period. The surface roughness measurement of plastics using atomic force microscopy was sensitive to the burial environment and demonstrates the potential of technique to measure relatively subtle changes to burial items when exposed to different environments conditions [77].

#### **3.9 Pressure sensitive adhesives analysis**

Pressure sensitive adhesive tapes are utilized for various purposes in criminal activities such as packaging of controlled drugs, the restraint of an individual during robbery and offences against a victim, the enclosure of explosive devices and for *Atomic Force Microscope in Forensic Examination DOI: http://dx.doi.org/10.5772/intechopen.104704*

**Figure 10.**

*Topography (a) and amplitude (b) maps offset from clearly visible is the interface between two different surface textures.*

concealment. To identify chemical constituents techniques such as Fourier transform infrared spectroscopy and pyrolisis–gas chromatography–mass-spectrometry are applied in forensic science laboratories for the discrimination of PSAs. However, AFM can offer supplementary and useful analytical data on PSAs as it has the capability to map the adhesives surface morphological and mechanical properties also AFM can give nanoscopic information. With respect to forensic application it holds the ability to interpret the physical data obtained from evidence found at a crime scene and linking it to a particular suspect [16]. **Figure 11** shows the AFM phase images for transparent cello, brown packaging tape and electrical insulation tape.

#### **3.10 Forensic analysis of fibres**

Fibers are an important trace evidence that can provide valued evidence to support an association of individual to a crime scene. Standard forensic examinations of man-made fibers usually involves microscopic techniques such as visible, polarized light and fluorescence microscopy as well as micro-spectrophotometry. Infrared spectroscopy is also used to identify the fiber polymer type present if two fibers are indistinguishable by microscopic techniques. Man-made fibers namely polyamides, polyacrylics and polyesters are analyzed using techniques such as FTIR, circular dicroism, Raman spectroscopy, differential scanning calorimetry, transmission electron microscopy and wide angle X-ray diffraction [78]. Forensic comparison of fibers is mainly focused on morphological analysis and spectral analysis. Shady Farah et al. in their study, analyzed polyethylene terephthalate (PET) fiber on three different materials such as plain fibers of pet, a common textile fiber and plastic material. They studied the morphological feature of the fiber using AFM [79].

The ability of the AFM to reconnoiter the nanoscopic morphological changes in the surfaces of fabrics was studied by Canetta et al. This study was focused on two natural namely cotton and wool and a regenerated cellulose (viscose) textile fibres. All the fiber samples were exposed to different environmental stresses for different lengths of times. The surface texture parameters of the environmentally stressed fabrics was measure quantitatively as a function of the exposure time from the obtained AFM images. In the AFM images the nanoscale the finest details of the surfaces of three weathered fabrics was clearly distinguishable between the detrimental

**Figure 11.** *AFM phase images for (a) transparent cello, (b) brown packaging tape and (c) electrical insulation tape.*

effects of the executed environmental conditions. The heights and roughness's of the unexposed and exposed fiber surfaces was measured by analyzing the obtained AFM images. **Figure 12** shows the AFM height images of cotton fibre exposed to loam and riverside soils, and pond and sea waters for 2 and 6 weeks. This study confirmed that the AFM can prove to be a very powerful tool in forensic examination of textile fibers to provide significant fiber examination as an evidence due to its proficiency of distinguishing between different environmental exposures or forced damages to fibers [80].

#### **3.11 Data recovery from damaged SIM cards**

In crimes involving digital evidences the data recovery plays very crucial role. Damaged SIM cards are highly useful evidence in such cases. The data obtained from such SIM cards give insights about the link between criminal and aids in future investigation. Nardi et al. used AFM for the enhancement and characterization of a forensically authenticated technique for sample processing and data extraction from a damaged SIM card. They develop a process to view the underside of the embedded EPROM/flash memory arrays present in smart card microcontrollers [81–83].

**Figure 12.**

*AFM height images of cotton fibre exposed to loam and riverside soils, and pond and sea waters for 2 and 6 weeks.*
