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FORENSIC INVESTIGATIONS DONE EASY AND FAST WITH THE LEICA DVM6 (REPORT NO. 2)

1709 views - 2018-10-22 13:30:47

Analyze Forensic Evidence Efficiently with Digital Microscopy


Digital microscopes [1] have no eyepieces and the image is observed directly on a monitor. They are very popular for a variety of applications in multiple fields [2, 3-8]. State-of-the-art digital microscopes, such as the Leica DVM6, allow an efficient workflow for forensic analysis.


Examples of how forensic scientists can gather evidence from hair, fibers, paint layers, explosive residues/small particles, and insects efficiently using the Leica DVM6 digital microscope are described in this report. It complements an earlier report on the use of digital microscopy in forensics for analysis of ballistics, tool marks, and counterfeited money, credit cards, and documents [2].


Certain functions of the Leica DVM6 enable users to gather and analyze data efficiently:


>> Simple, rapid way to change magnification over the entire range with 16:1 zoom and easy objective change [5]
>> Intuitive Leica Application Suite (LAS) X software for microscope operation and data analysis [5]
>> Large mosaic overview of the sample with XYZ stitching [6, 7]
>> Images with large depth of field in sharp focus using the extended depth of field (EDOF) multi-focus capability [5, 6]
>> Automated tracking and storing (encoding) of important parameters [5]
>> Fast, one-handed microscope head tilting and sample rotation [4, 5, 7]
>> Integrated ring light and coaxial illumination plus accessories for various contrast methods [3, 4, 7]
For further details about the Leica DVM6 digital microscope, please refer to the previous report on forensics [2] or the Leica DVM6 product page [9]

 

 

Hair and Fibers


Hair and fiber evidence obtained from crime scenes [10, 11] are often imaged and analyzed with a microscope [10-13]. The Leica DVM6 digital microscope can provide high quality images of hair or fiber samples under investigation quickly and easily. Images of human and animal hair and fibers in a textile sample taken with the Leica DVM6 are shown over the next two pages.

 

 

Human Hair
The human hair is composed of a shaft with three major features: medulla (central core), cortex (middle layer), and cuticle (outer layer) [11, 12]. The hair’s root grows from the follicle which is part of the scalp [11, 12].
Frequently, the medulla and cuticle are analyzed. In human hairs, the medulla is either continuous, interrupted, fragmented, or absent and the cuticle has an imbricate (flattened scale) structure [11, 12]. If a hair strand with its root intact is found to contain tissue from the follicle, it can be used for DNA analysis [11, 13].
Leica DVM6 images of various human hairs, recorded using the extended depth of field (EDOF) or multi-focus mode, are seen here in figures 1-6.

 

  

 

  

 

Animal Hair


The medulla of animal hairs often occupies a much larger volume of the shaft, known as the medulla index [11, 12], compared to human hairs. The cuticle of animal hairs can be coronal (crown-like scales), spinous (petal-like scales), or imbricate as noted above for humans [11, 12]. Leica DVM6 images (multi-focus mode) of an otter and sheep hair are shown in figures 7 and 8 below.

 

 

 

Fibers


Fibers are the smallest components of textiles. They can be natural from plants, insects, or animals, such as cotton, silk or wool, or synthetic from polymers, such as nylon or polyester [11, 14]. Textile fibers found at a crime scene can be transferred from the surroundings or victim onto the perpetrator during physical contact [11, 14]. Forensic analysis of such fibers can find unique characteristics or traits which help to identify and match them. Below in figures 9-12 are some Leica DVM6 images of a textile sample composed of nylon. Figure 13 shows a line profile measurement made in the multi-focus image of figure 12.

 

 

Paint


Property damage found at crime or accident scenes is often analyzed in forensic investigations [15, 16], e.g., painted metallic surfaces of automobiles, buildings, etc. There can be subtle, yet unique differences in the paint coatings of automobiles, especially in relation to the manufacturer and model. These differences make it possible to match paint evidence with a specific automobile or type of automobile [15, 16]. Paint chips found at a crime or accident scene can be imaged and its multiple layers analyzed with microscopy to identify some  of its unique characteristics. Leica DVM6 images of a paint chip are shown in figures 14-17 below.

 

 

Explosive Residues / Small Particles


Forensic investigations can also involve the study of residues from explosions which have occurred at crime or accident scenes [17, 18]. Typically, these residues are composed of small particles created by fragmentation of the explosive device itself or nearby objects [19,20]. Swabbing areas around the center of the explosion is a way to collect these residue particles [17,18]. The explosive residue swabs are often imaged and analyzed with microscopy, among other techniques. The images in figures 18 and 19 below of swab samples were taken with a Leica DVM6.

 

Insects: Forensic Entomology


Forensic entomology is the study of insects and arthropods found at crime scenes, usually in relation to death investigations [21-23]. The insects most often found on and around a corpse are flies and beetles. The presence of a particular species of fly or beetle usually correlates with the time since death [21- 23].

As is also the case in general entomology, samples of insects and arthropods collected during forensic investigations can be identified from their anatomy via microscopy imaging. Leica DVM6 images of a green blow or bottle fly, a species commonly found on a corpse shortly after death [21-23], are shown in figures 20 and 21 on the right.

 

 

Summary

 

Summary table showing which features of the Leica DVM6 are useful for certain forensic analyses [9]. An X means the feature is “useful” for the particular analysis.

 

 

Magnification

Illumination

Observation Perspective

3D-Imaging

2D-Imaging

 

 

 Low Objective

Middle Objective

High Objective

Integrated Ring / Coaxial Light

Spotlight (LED5000 SLI)

Transmitted Light (BLI)

Tilting

Rotating

Extended Depth of Field (Infinite Focus)

X-Y Stitching (Scan)

Leica DVM6 S

 

 

 

 

 

 

 

 

Z image builder

 

 

XYimage builder

 

Leica DVM6 A

 

 

 

 

 

 

 

 

 

montage

3D models

 

mosaic

Hair and Fibers

 

X

X

X

X

X

 

 

X

X

X

 

 

Paint Chips

X

X

X

X

X

 

X

X

X

X

X

 

 

Explosives

X

X

X

X

X

 

X

X

X

X

 

 

 

Particles

X

X

X

X

X

 

X

X

X

X

 

 

 

Soil

X

X

X

X

X

 

X

X

X

X

 

 

 

Glass

X

X

X

X

X

X

X

X

X

X

 

 

 

Entomology

X

X

 

X

 

 

 

 

X

X

X

X

X

 

 

Conclusions


The exemplary images show the use of the Leica DVM6 digital microscope for forensic analysis of evidence from hair, fibers, paint layers, explosive residues, and insects (entomology). A fast, efficient workflow for analysis of forensic evidence is accomplished due to the practical features of the Leica DVM6, e.g., a convenient way to change magnification rapidly over the full range, one-handed tilting and sample rotation, intuitive software for microscope operation and data analysis, and versatile illumination. An efficient workflow leads to efficient data acquisition and analysis for forensic investigations.

 

Additional Reading

  

1.           J. DeRose, G. Schlaffer, WhatYou Always Wanted to Know About Digital Microscopy, but Never Got Around to Asking,Science Lab
 
2.           J. DeRose, M. Doppler, Forensic Investigations Made Easy and Fast with Digital Microscopy Part 1: ballistics, tool marks, questioneddocuments,counterfeiting,forgery,ScienceLab
3.           J. DeRose, G. Schlaffer, Digital Microscopy with Versatile Illumination and Various Contrast Methods for More Efficient InspectionandQualityControl:Exampleapplications using the Leica DVM6 with integrated ring light or coaxial illumination system,ScienceLab
4.           J. DeRose, G. Schlaffer, AutomotiveIndustry:Rapid and Precise Surface Inspection on Hard-to-Image Samples,LeicaMicrosystemsWebsite
5.           J. DeRose, G. Schlaffer, MicroelectronicsTechnical Report Part 1: Inspecting and Analyzing Printed Circuit Boards Quickly andReliably with a Digital Microscope,Leica DVM6 Product Page
6.           J. DeRose, A. Reinhold, G. Schlaffer, Automotive Industry: HowSuppliers and Auto Manufacturers Can Verify Parts Specifications Quickly and Easily Inspecting and Documenting Automotive Parts with Digital Microscopy, ScienceLab
7.           J. DeRose, G. Parma, FastandReliable Inspection of Printed Circuit Boards with Digital Microscopy, ScienceLab
 
8.           J. DeRose, M. Doppler, WhatDoes30,000:1 Magnification Really Mean? Some Useful Guidelines for Understanding Magnification in Today’s New Digital Microscope Era,ScienceLab
9.           LeicaDVM6ProductPage,Technical Specifications,LeicaMicrosystemsWebsite
 
10.      D.W.Deedrick,FederalBureauofInvestigation(FBI)ForensicScienceCommunications,Hairs, Fibers, Crime, and Evidence Part 3:Crime and Evidence,vol. 2, no. 3, July 2000,
11.      D.Nivens, CHEM 4600 Special Topics: ForensicChemistry,ArmstrongStateUniversity
 
12.      D.W.Deedrick,FederalBureauofInvestigation(FBI)ForensicScienceCommunications,Hairs, Fibers, Crime, and Evidence Part 1: Hair Evidence, vol. 2, no. 3, July 2000,
13.      J.M. Moore, A.R. Isenberg, Federal Bureau of Investigation (FBI) Forensic Science Communications, MitochondrialDNAAnalysisattheFBILaboratory,vol. 1, no. 2,July 1999
14.      D.W.Deedrick,FederalBureauofInvestigation(FBI)ForensicScienceCommunications,Hairs, Fibers, Crime, and Evidence Part 2:FiberEvidence,vol. 2, no. 3, July 2000
15.      ScientificWorkingGrouponMaterials Analysis (SWGMAT), Federal Bureau of Investigation (FBI) Forensic Science Communications, ForensicPaint Analysis and Comparison Guidelines, vol. 1, no. 2,July 1999
16.      C.Muehlethaler, L. Gueissaz, G. Massonnet, ForensicPaint Analysis, Section: Chemistry/Trace/Paint and Coating, Encyclopedia ofForensic Sciences, 2nd Ed.(Elsevier, 2013) pp. 265–272, ISBN: 978-0-12-382166-9, doi: 10.1016/B978-0-12-382165-2.00109-4

17.     J.G. McDonald, D.E. Maslanka, K.H. Mount, M.L. Miller, Federal Bureau of Investigation (FBI) Forensic Science Communications, DevelopmentandTesting of a Solid Phase Microextraction Method for the Trace Analysis of Nitro Organic Explosives Using GasChromatography-ElectronCaptureDetectorandGasChromatography-MassSpectrometry,vol. 6, no. 4,October2004
18.     T.Tamiri,S.Zitrin,Explosives:Analysis,Section:Chemistry/Trace/Explosives,EncyclopediaofForensicSciences,2ndEd.(Elsevier,
2013) pp. 64–84, ISBN: 978-0-12-382166-9, doi: 10.1016/B978-0-12-382165-2.00083-0
                                                                            
19.     J.D. Kelleher, Federal Bureau of Investigation (FBI) Forensic Science Communications, ExplosivesResidue: Origin and Distribution,vol. 4, no. 2, April 2002
20.     J. Crippin, Explosions,Section:Chemistry/Trace/Explosives,EncyclopediaofForensicSciences,2ndEd.(Elsevier, 2013) pp. 104–
108,ISBN: 978-0-12-382166-9, doi: 10.1016/B978-0-12-382165-2.00085-4
 
21.     G.S.Anderson,ForensicEntomology:TheUseofInsectsin Death Investigations
 
22.     I.Joseph,D.G. Mathew, P. Sathyan, G. Vargheese, Theuseofinsectsin forensic investigations: An overview on the scope offorensic entomology, Journal of Forensic Dental Sciences, vol. 3, iss. 2,pp.89-91(2011),doi: 10.4103/0975-1475.92154
23.     J. Wiesner, M. Benecke, EvenInsectFragmentsThrowLightonHowCrimesAreCommitted:HowForensicBiologist Dr. MarkBeneckeGains Insights,ScienceLab
 
 

Insects: Forensic EntomologyForensic entomology is the study ofinsects and arthropods found at crimescenes, usually in relation to deathinvestigations [21-23]. The insects mostoften found on and around a corpse areflies and beetles. The presence of aparticular species of fly or beetle usuallycorrelates with the time since death [21-23].As is also the case in general entomology,samples of insects and arthropodscollected during forensic investigationscan be identified from their anatomy viamicroscopy imaging. Leica DVM6 imagesof a green blow or bottle fly, a speciescommonly found on a corpse shortly afterdeath [21-23], are shown in figures 20 and21 on the right.

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