# data[].attributes.body
Joicelyn M.

# data[].attributes.attachment_link.readable_text
Glass is the most frequently occurring transfer evidence found at crime scenes. Generally, it is encountered in scenes involving burglary, hit and run, shooting scenes and housebreaking and theft etc. Broken glass is easily transferred to objects and individuals present at the scene of crime, thus it is possible to link a suspect to the event and the items as well as to the individuals present at crime scene [1]. Glass analysis mainly involves classification, discrimination and individualization of the glass evidence [2]. Classification can also be called identification. As different kinds of evidence samples may be encountered at the same crime scene it is important to identify the exact source of that evidence sample. Discrimination comes after classification, as it excludes the evidence if it does not match the source. Individualization is a determination process that every sample is unique even among other samples of same class. According to the law of individuality, every evidence sample have unique characteristics that differentiate it from the class of evidence. Physical matching is the only method of glass individualization. Physical matching of the known broken sample fragments with the questioned sample enables the individualization of glass evidence and eliminates all other sources [2]. In case if physical matching is not possible then other methods of analysis are performed. Other forensic analysis of glass consists of comparison of various physical properties, optical properties and elemental analysis techniques [3].

History of forensic analysis of glass evidence

Various kinds of glass evidences can be encountered at the crime scene such as small glass fragments, broken glass pieces, window planes, headlights, etc. Every glass has different composition and that plays important role in the forensic analysis of glass. Glass has different kinds of fractures and forensic analysis can determine the direction of glass fracture. Early forensic analysis includes physical techniques, microscopic techniques and elemental analysis.

Physical examination: Every glass analysis starts with identification of the glass by physical and optical properties such as amorphous structure and isotropism, hardness. Initial stages of analysis involve physical observation such as colour, surface feature, fluorescence and thickness of the glass sample. Physical examination plays important role in the comparison process of glass evidence recovered from the scene of crime and the questioned sample [4].
Basic schematic diagram for glass analysis
Density and refractive index measurements are conventional methods that were first used in glass analysis. Most forensic science laboratories use Sink-float method to determine density. In this method, a questioned glass fragment is dropped into a liquid mixture of bromobenzene and bromoform. If the glass density matches the liquid mixture density, the glass fragment neutrally floats in the liquid mixture. This method had some demerits, thus an alternative method for the determination of density is derived which is based on Stoke's law [5].

Refractive index (RI) has been determined by immersion method in the initial years of forensic glass analysis. This method of determining RI was based on the technique described by Winchell and Emmons in 1926. This method involves, a glass fragment being immersed in a suitable oil and then heating until the glass observed under a microscope disappeared. At this temperature refractive index of both oil and glass fragments is the same [3].

Microscopic techniques re used for the preliminary examination of surface features of glass fragments. Light microscopes and stereo-microscopes are used widely for this purpose. Light microscopes are used to identify the layers of glass fracture. Glass fragments are first visually examined under fibre optical light and then observed under stereo-microscope [6].

Elemental analysis is the confirmatory examination for determining the chemical texture of glass evidence. Most of the elemental analysis are destructive in nature. Elemental analysis includes neutron activation analysis, atomic absorption spectroscopy, scanning electron microscopy (SEM), inductive coupled plasma spectroscopy (ICP), etc.

which were primarily used in the initial days of glass analysis.

Present day forensic analysis of glass

Basic steps of forensic glass analysis are same in the present day as well. Parameters of glass examination are same only the methods of examination are evolved. Physical matching or jig-saw method is still in use. Measurement of density is reduced in present days due to its limitations but still, it performed in some of the laboratories [2]. Density gradient tube filled with liquid has been discovered for the determination of density. Method of determination of refractive index has been evolved in the new era. Glass refractive index measurement (GRIM) is an automated system for determining refractive index using the immersion method. Emmons procedure has been developed for the determination of refractive index. This method uses a hot-stage microscope in association with different source lamps [1][7]. Microscopic advancement has been increased in recent years which helps in the preliminary examination of glass evidence. Elemental analysis has highly emerged in the present day. Nowadays scanning electron microscopy in conjugation with energy dispersive x-ray spectroscopy (SEM-EDX) is primarily used for elemental analysis of glass [8]. Conventional method inductive coupled plasma (ICP) spectroscopy has some disadvantages and to overcome these disadvantages ICP is coupled with optical emission spectroscopy (OES) [ICP-OES], and ICP-OS is also coupled with mass spectroscopy [ICP-OES-MS] for better result [2][9]. Laser ablation inductive coupled plasma mass spectroscopy [LA-ICP-MS] has been discovered for the detailed elemental analysis of glass [10].

Future forensic analysis of glass

According to the present scenario, the glass industry is manufacturing advanced glasses which will need more advanced techniques for glass analysis. Glass manufacture process has been evolved over the last few years. Conventional glass composition varies with modern-day glass composition. As with changing and emerging composition of glass, method of its elemental analysis is also emerging. In the future glass analysis will not be limited to present-day technologies. Researches in the field of elemental analysis are witnessing new advancement like total reflection x-ray fluorescence (TRXRF), scanning electron microscopy x-ray (SEM-XRDF) diffraction techniques, etc. [2].

Case study: Susan Nutt (1987)

In February 1987, Craig Elliott Kalani 19-year old killed in a hit-and-run case. He went for a night walk along with his dog in his neighbourhood in northwest Oregon at 9:30 PM, but never returned to his home. As the investigation proceed police found some glass pieces near his body and some of the glass fragments in Craig's pocket.

After the collection of glass fragments, police started to search a vehicle that had damages consistent with a hit and run case. They found a car with a similar kind of damages to a woman named Susan Nutt. In order to connect Susan to the crime, it was needed to match those damages of the car to the glass fragments found at crime scene. During forensic analysis, analyst found that the glass fragments from the crime scene matched the Susan's car damages in a preliminary examination i.e., Physical match. During elemental analysis, analyst found that windshield glass from the crime scene and Susan's car contained the same 22 chemical elements. And that concluded that the glass fragments found at the crime scene belonged to Susan's car.

The glass evidence helped to convict Susan Nutt. She was sentenced to up to five years in prison and five years in probation.

Glass has been used as evidence in criminalistics for over a century and its evidentiary value is still increasing day by day. The face of forensic analysis of glass has been changing over recent years due to advances in the identification of physical matching, physical and optical properties and elemental analysis. Advancement in forensic glass analysis has been reached the next level in the modern era and it will keep enhancing in upcoming years.

1. Forensic glass analysis James E. Girard - Criminalistics: forensic science, crime and terrorism 2nd 97-112

2. The forensic analysis of glass evidence: past, present, and future BW Kammrath, AC Koutrako - Forensic Science: A multidisciplinary approach, 2016 - books.google.com 299-329.

3. Elemental analysis of glass and paint materials by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for forensic application Tatiana Trejos, Waleska Castro, Jose r. Almirall October 2010 - 17-19.

4. Forensic Glass Comparison: Background Information Used in Data Interpretation Maureen C. Bottrell April 2009 vol 2 no. 2. (https://archives.fbi.gov/archives/about-us/lab/forensic-science-communications/fsc/april2009/review).

5. Density determination of irregular shaped and small glass fragments by Stoke's law: An alternative technique for the forensic analysis of glass Panadda, C. Ratchapak and P. Nathinee 2018.

6. Microscopic analysis methods https://www.contractpharma.com/issues/2014-10-01/view_features/using-microscopical-analysis-methods/ (Last accessed on 24-10-2021)

7. Forensic classification of glass employing refractive index measurement Umi K. Ahmad, Nur F. Asmuje, Roliana Ibrahim, Nor U. Kamaruzaman. Malaysian journal of Forensic Science 2012, 3(1).

8. A Review of Scanning Electron Microscopy Investigations in Tellurite Glass Systems Ali E. Ersundu, Miray Celikbilek, Suheyla Aydm 2012.

9. Analysis of major elements in glass sample with a sequential ICP- OES Jobin Yvon S.A.S Horiba Group, Longjumeau, France.

10. 10 modern technologies in forensic science https://www.forensicscolleges.com/blog/resources/10-modern-forensic-science-technologies (Last accessed on 24-10-2021)

11. Forensic glass analysis by LA-ICP-MS: assessing the feasibility of correlating windshield composition and suppler Abbegayle J. Dodds, Edward M. "Chip" Pollock, Donald P. Land October 2010.

12. https://prezi.com/fj2a8w7v6fbu/craig-elliott-kalani-hit-run/ (Last accessed on 29th October 2021).

# data[].attributes.attachment_link.title
Forensic analysis of glass evidence: Past, Present and Future

# data[].attributes.attachment_link.description
Introduction Glass is the most frequently occurring transfer evidence found at crime scenes. Generally, it is encountered in scenes involving burglary, hit and run, shooting scenes and housebreaking and theft etc. Broken glass is easily transferred to objects and individuals present at the scene of crime, thus it is possible to link a suspect to [...]

# data[].attributes.body
Joicelyn M

# data[].attributes.body
Kariem Lane

# data[].attributes.body
Kariem Lane

# data[].attributes.body
Joicelyn M.

# data[].attributes.attachment_link.readable_text
No subscription required

Want another evidence packaging activity?

Where have you been?

In forensics, Locard's Exchange can be summed up as the principle that any time you have contact with another person, place or thing, you leave something behind and you take something away with you.

For criminal investigations, that means the perpetrator leaves evidence behind at a crime scene (e.g., a fingerprint, a hair, etc.) and also takes something from the crime scene away with them (e.g., a carpet fiber, a pet hair, etc.).

That evidence can be used to connect a suspect to a crime scene.

For more information, see The Cornerstone of Forensic Science: Locard's Exchange Principle by Douglas P. Lyle
Ready to try it for yourself?
You can do this activity on your own, or divide into teams and examine the other team's evidence.

1. Get a freshly laundered t-shirt.

2. Examine the t-shirt for any trace evidence like hairs or fibers. If you find any, remove them.

3. Wear the t-shirt for four hours or longer and do the same things you usually do. Keep track of where you go and what you do during the time you're wearing that t-shirt.

4. Remove the shirt (and exchange with the other team, if there is one).

5. Examine the shirt under a bright light.

6. List all the evidence you can find like hairs, fibers, stains, etc.

7. Collect as much of the evidence as you can following the procedure.

8. Write down your theory of where each evidence item came from (the neighbor's cat, the classroom/office carpet, etc.)

9. Compare your list of theories with the t-shirt wearer's log of activities. Were your theories accurate?

Evidence Bags Sample Pack

Evidence Box Sealing Tape, Red

Evidence Packaging Kit

# data[].attributes.attachment_link.title
Evidence Packaging - ForensiKit by Crime Scene

# data[].attributes.attachment_link.description
Learn the basics of evidence packaging with ForensiKit by Crime Scene. Go hands-on with the same supplies the professionals use.

# data[].attributes.body
Kariem Lane

# data[].attributes.body
Joicelyn M.

# data[].attributes.body
Kariem Lane

# data[].attributes.attachment_link.readable_text
When collecting a known comparison sample, take samples directly from the source of broken glass, if possible. Take comparison samples from the ground only when there is no glass remaining at the source. Select a comparison sample from each possible source (ie: different window panes). Collect a comparison sample no smaller than a quarter and no larger than a sheet of paper. Package samples separately from one another as described below, labeling them appropriately.

Glass fragments may contain fingerprints and therefore should be handled as little as possible and with gloved hands, handling the edges of the glass if possible.

​

If the glass will also be examined for ignitable liquid residue (for example, if it is part of a Molotov cocktail), please consult the laboratory for the proper collection procedure. Items should not be air-dried or packaged in an air-permeable container if they will be examined for ignitable liquid residue.

Fracture matching may be possible. Comparison of elemental and optical qualities of glass between known and questioned samples can be done to determine if they could have originated from the same source.

Glass window panes can be reconstructed in an attempt to determine the direction of force applied to cause the break or the order in which consecutive breaks were made (ie: which break was made first).

# data[].attributes.attachment_link.description
When collecting a known comparison sample, take samples directly from the source of broken glass, if possible. Take comparison samples from the ground only when there is no glass remaining at the source. Select a comparison sample from each possible source (ie: different window panes).

# data[].attributes.body
Kariem Lane

# data[].attributes.attachment_link.readable_text
Recent research efforts in the forensic trace field have focused on the development of databases to assign a significance to forensic evidence (i.e., to report the strength of an association or exclusion). In the forensic analysis of glass using µ-XRF, samples are typically compared using element intensity ratios. However, because of differences in instrumentation, the development of a database compiled with element ratios collected by different laboratories is not currently feasible. The collection of quantitative XRF data will address this limitation. Thus, this project focuses on the development of a quantitative XRF glass database that can be used by forensic practitioners to assign a significance to forensic glass evidence.

The forensic community uses several glass standards and reference materials from NIST and abroad that are currently low in stock. Additionally, the community relies on published consensus values or on certified values that were collected more than 20 years ago and at sampling scales that are not relevant to the forensic community. This project aims to address these gaps by (1) reanalyzing elemental concentration (at trace and bulk sampling scales) for several commonly used glass SRMs with modern instrumentation and methods ( i.e., LA-ICP-MS), and (2) collaborating with Dr. Almirall's group at Florida International University to aid in the design and assessment of three new reference glasses.

Although the forensic community has reached a consensus on the analysis of glass evidence using LA-ICP-MS, there is currently no standardized method for the interpretation of glass evidence. Recent efforts in the community have focused on the use of databases to provide a significance to glass evidence using more objective approaches (e.g., likelihood ratio). This collaborative project, organized by Dr. Almirall's group at Florida International University, involves an inter-laboratory study, designed as a mock forensic case, that aims to evaluate the performance of the likelihood ratio for the interpretation of glass evidence.

# data[].attributes.attachment_link.description
The goal of this focus area is to improve the field of glass evidence analysis by developing new matrix-matched glass standards and by evaluating more objective approaches to evidence interpretation, such as the likelihood ratio. The latter will be accomplished through the development of glass databases that may be used to assign a significance to an association or exclusion in forensic casework.

# data[].attributes.body
Kariem Lane

# data[].attributes.attachment_link.readable_text
Syracuse, NY -- Prosecutors spent much of today showing the jury evidence from 29 years ago in the murder trial of Ronald Meadow, accused of strangling his estranged wife, Colleen.

Among the mounds of evidence, there was a glass wine decanter, a clock radio and hair samples, all kept in evidence bags after being collected from the March 5, 1985 murder scene. During testimony, Assistant District Attorney Robert Moran walked the officer who supervised the evidence collection through the process.

Now retired, Drew Buske relied heavily on his notes from the time to recall what the items were. Some of the dozens of items directly related to the prosecution's case against Meadow, others were simply items collected that helped paint a picture of the victim's life and her Syracuse apartment.

Onondaga County District Attorney William Fitzpatrick is the lead prosecutor in the trial against Meadow, who was arrested late last year for the cold-case murder of his wife, Colleen, in her Syracuse apartment in 1985. She was found hog-tied and face-down on the floor.

Defense lawyer Ed Menkin was quick today to point out problems with the three-decade-old evidence.

The glass wine decanter had shattered. No one knows how. Buske speculated someone had dropped it. Menkin guessed that was probably true.

The clock radio, clearly seen in crime scene photos at 10:01 p.m., had mysteriously advanced to 10:03 since then. Menkin guessed it had been plugged in at some point; Buske said he didn't know.

And "tape lifts" were used to collect hair from the scene for identification. Now, much better DNA technology is available.

All in all, Menkin's cross-examination highlighted the problems with relying on evidence so old and, in some cases, mishandled.

Fitzpatrick acknowledged in his opening statements that police standards in the 1980s were not as exacting as they are today. Technology wasn't as advanced. Some evidence wasn't collected properly. But he told the jury that didn't keep him from proving the case.

Menkin spent a long time trying to poke holes in the veracity of the evidence introduced today, trying to cast doubt on the prosecution's case.

The evidence had been moved several times since 1985. Sealed bags had been opened and re-opened. Officers had little to no recollection of the scene outside of their notes.

At the end of the day, Fitzpatrick called Colleen Meadow's sister, Nancy Moran, to the witness stand.

She said that Colleen described on several occasions Ron beating her. One time he beat her sister, Moran said, was when they were on a trip. Ron didn't like the way she was driving, so he got in the driver's seat and punched her, Moran testified her sister had told her.

Moran never saw Ron Meadow abuse Colleen, she said. But Moran is the third person to say that Colleen Meadow had confided in them about her husband's abusive behavior.

Colleen's aunt said Tuesday that Colleen told her about Ron Meadow handcuffing her to a chair early in their marriage. And her boss at Niagara Mohawk said Colleen told her that Ron had threatened to kill her.

Each of those times, County Court Judge Anthony Aloi told the jury they could consider that testimony as evidence of the couple's relationship and Ron Meadow's potential motive. But they could not consider that to mean the defendant had a propensity or predisposition to commit murder.

Testimony resumes at 9:30 a.m. Thursday.

# data[].attributes.attachment_link.title
Evidence in cold-case murder trial: Shattered glass and a clock that's gone 2 minutes in 29 years

# data[].attributes.attachment_link.description
Syracuse, NY -- Prosecutors spent much of today showing the jury evidence from 29 years ago in the murder trial of Ronald Meadow, accused of strangling his estranged wife, Colleen. Among the mounds of evidence, there was a glass wine decanter, a clock radio and hair samples, all kept in evidence bags after being collected from the March 5, 1985 murder scene.

# data[].attributes.body
Joicelyn M.

# data[].attributes.attachment_link.readable_text
Forensic analysis of glass consists of the examination of two or more fragments to determine whether they have a common origin. Identifying broken glass fragments having a common source to the exclusion of all other sources may only be done if they can be physically matched together.

Submitted samples from a crime scene must first be confirmed as glass. Differentiating glass from plastic is done by examining relative hardness, solubility, and observation with a polarized light microscope. Once confirmed as glass, the examiner will perform an analysis of physical properties (color, fluorescence, thickness, curvature, density), optical properties (Refractive Index) and chemical composition. If a difference between questioned and known samples is found at any point in this process no further comparison is needed.

Reference: Scientific Working Group on Materials Analysis, "Initial Examinations of Glass", July 2004, accessed March 10, 2016.
View PDF
NCFS Research:

1. Characterization of float glass by laser-induced breakdown spectroscopy (LIBS)

2. Forensic comparison of glass by laser-induced breakdown spectroscopy (LIBS)

3. Comparison of float glass by application of chemometrics to LIBS data.

For more information contact Dr. Michael Sigman and Dr. Matthieu Baudelet.

# data[].attributes.attachment_link.description
Forensic analysis of glass consists of the examination of two or more fragments to determine whether they have a common origin. Identifying broken glass fragments having a common source to the exclusion of all other sources may only be done if they can be physically matched together.

# data[].attributes.body
Joicelyn M.

# data[].attributes.attachment_link.readable_text
When collecting a known comparison sample, take samples directly from the source of broken glass, if possible. Take comparison samples from the ground only when there is no glass remaining at the source. Select a comparison sample from each possible source (ie: different window panes). Collect a comparison sample no smaller than a quarter and no larger than a sheet of paper. Package samples separately from one another as described below, labeling them appropriately.

Glass fragments may contain fingerprints and therefore should be handled as little as possible and with gloved hands, handling the edges of the glass if possible.

​

If the glass will also be examined for ignitable liquid residue (for example, if it is part of a Molotov cocktail), please consult the laboratory for the proper collection procedure. Items should not be air-dried or packaged in an air-permeable container if they will be examined for ignitable liquid residue.

Fracture matching may be possible. Comparison of elemental and optical qualities of glass between known and questioned samples can be done to determine if they could have originated from the same source.

Glass window panes can be reconstructed in an attempt to determine the direction of force applied to cause the break or the order in which consecutive breaks were made (ie: which break was made first).

# data[].attributes.attachment_link.description
When collecting a known comparison sample, take samples directly from the source of broken glass, if possible. Take comparison samples from the ground only when there is no glass remaining at the source. Select a comparison sample from each possible source (ie: different window panes).

# data[].attributes.attachment_link.readable_text
Glass is a hard, brittle, amorphous substance obtained by fusing a mixture of silica and two or more alkaline bases, such as soda, lime or potash. It is also contains certain amount of various other elements and metals as impurities or may have been added for obtaining color, degree of hardness, heat resistance glass etc.

Glass as a physical clue, frequently encountered in various crimes such as road accidents, murder, hit and run, sexual assaults, arson and vandalism. Thus glass is one of the important evidence in many criminal investigations.

METHODS OF EXAMINATION OF GLASS

The forensic examination of glass could also be undertaken in two steps. One is that the physical comparison of suspected and control glass fragments and their source and secondly, the examination of glass fractures on fragments and their reconstruction for determining the direction and sequence of impact of projectile.

PHYSICAL COMPARISON FOR EXAMINATION OF GLASS

1. APPEARANCE- transparent/ milky/ ground/ colored.

2. Type of glass- ordinary/ borosilicate/ laminated/ pyrex/ automobile glass etc.

PHYSICAL MEASUREMENTS OF EXAMINATION OF GLASS

Cracked glass. Broken window, shattered glassy surface and break windshield glass texture silhouette. Crack shattered mirror or bullet hole. Vector illustration isolated icons set

The physical examination of glass includes two mainly parameters namely, the thickness and curvature of glass pieces under examination of glass evidence. The thickness of glass sheet varies significantly from one place to another place and do not uniform throughout.

1. EDGE THICKNESS: a micrometer is employ to measure accurately the edge thickness of the glass fragments. Reading should be taken all around the broken edged to find out at which point, the crime exhibits matches with any portion of the broken glass.

2. CURVATURE: a spherometer is used to measure the radius of curvature of the glass fragments having curved surfaces. The radius of curvature of the fragments is calculated using the formulae.

R= (l²/6h)+(h/2)
Where,

l= the mean distance between the legs of spherometer.

h= height of the curved surface.
FLUORESCENCE UNDER UV RADIATION
Some types of glass fluorescence under ultraviolet radiation with different colors such as brown, violet, purple, blue or green etc. it is considered to be one of the rapid, non-destructive and reliable method for examination of glass. This examination of glass has to e conducted in a dark room and the glass pieces to be exposed to UV radiation should be of similar size and thickness and they are to be thoroughly washed with acetone or any other solvent to remove grease or dirt.

When there is a clear difference in fluorescence of the two glasses, it indicates different sources of their origin. On the other hand, the similarity in fluorescence by itself cannot be proof of similar source and further tests are to be conducted to arrive at the possible commonness of origin.

PHYSICAL MATCHING OF FRAGMENTS

The most conclusive evidence of the source of a piece of broken glass is an exact fit with a broken edge of the original glass. It is done in much the same way in which a jigsaw puzzle is put together. The sizes of fragments, their shapes, and therefore the fractured edges are moved around until the edges of the given pieces are found to correspond.

DENSITY OR SPECIFIC GRAVITY
The physical properties of density and index of refraction are used most successfully for characterizing glass particles. The characterizing properties of glass depend not only on the constituent elements, but also on the manner in which the glass has been treated during manufacture. However, these properties are class characteristics, which cannot provide the sole criteria for individualizing glass to common source. If the density and refractive index values are not comparable, this certainly excludes the possibility that the glass fragments originated from the same source.

Glass from various sources such as windowpane, automobile headlights, bottles and plate glass doors, all have slightly different densities. The density of various glass and related materials are given below:

Window glass, flat - 2.47 to 2.56

Head light glass-2.47 to 2.63

Mica - 2.6 to 3.2

Flint, glass- 2.9 to 5.9

a. Density comparison by floatation method

1. The crime and control glass piece samples are crushed to comparable sizes with similar shapes which is one of the most important steps in examination of glass density. Each piece of glass is sketched and marked.

2. A clean and dry sample of crime glass particle is placed in a small beaker containing bromoform (heavier liquid). The glass will float on the liquid surface indicating that density of the liquid is greater than that of the glass.

3. Slowly add the less dense liquid, bromobenzene, drop wise with stirring, until the particle is exactly suspended. One should be careful while adding the mixture that it should be stirred with each addition so that air bubbles, of any are removed.

4. Added similar size, clean and dry sample of control glass. If both the crime and control glass particles are suspended in the liquid, then the density of both the glass particle is same to that of the liquid mixture. Particles with different densities will either sink or float depending upon whether they are denser or less dense than the liquid medium.

5. The densities o the particle of the glass can be determined by calculating density/specific gravity by floatation mixture using specific gravity bottle or a pycnometer.

b. DENSITY BY DENSITY GRADIENT TUBE

Density gradient method is good method for examination of glass fragments, when there are a number of glass fragments that is several unknown samples.

1. In this method, vertical glass tube about 5mm in internal diameter and 10-18 inches long is sealed at one end and filled with successive layers of liquid in decreasing density.

2. Gradient is such that the density at any level is less than that of any lower level within the tube and greater than that of any level higher within the tube.

3. The standard gradient tube is made up of layers of two liquids mixed in varying proportions, so that each layer has a different density.

4. When completed a density gradient tube usually has 6-8 layers.

5. Place seven test tubes in a test tube rack.

6. Prepare the mixtures of bromobenzene and bromoform in the following ratios, by pipetting out the respective liquids into the test tubes:

7. Pure bromoform - 6ml

8. 1ml of bromobenzene and 5 ml of bromoform

9. 2ml of bromobenzene and 4 ml of bromoform

10. 3 ml of bromobenzene and 3 ml of bromoform

11. 4 ml of bromobenzene and 2 ml of bromoform

12. 5 ml of bromobenzene and 1 ml of bromoform

13. 6 ml of bromobenzene

14. The glass fragments should be carefully and gently placed in the tube and allowed to settle down. These fragments will settle down in the portions having the same density.

15. Thus, the density of the liquid and hence of the fragments can be determined.

REFRACTIVE INDEX
Every material has its own refractive index. The refractive index measurement can give an indication of the composition and thermal history of the glass.

Refractive index is a dimensionless quantity which is characteristic of an optical medium and is defined as the ratio of the velocity of light in a vacuum to the velocity of light in the medium.

n=c/v

where, n- refractive index of the medium

c- Velocity of light in vacuum

v- velocity of light in a medium

a. RFRACTIVBE INDEX BY IMMERSION METHOD

When a transparent object such as glass is immersed in a liquid of same refractive index, it will be invisible because of optical homogeneity of the system. A simple procedure for examination of glass refractive is as follow:

1. Place the glass fragment in a small beaker, after cleaning and drying.

2. Select suitable liquids from the following:

Di-n-butyl carbonate- 1.411

Tri-n butyl citrate - 1.45

Alpha- bromonaphalene - 1.658

Methylene iodide - 1.742

3.Add liquid of lower index than glass in a sufficient quantity to cover the glass piece.

4.Now, add in small amounts, the liquid of higher refractive index, until the glass becomes invisible.

5.Remove the sample of the liquid and determine its index of refraction using an abbe refractometer.

b. REFRACTIVE INDEX USING BECKELINE METHOD

The image of a transparent object observed through a microscope is made by refraction and reflection. Thanks to this behavior of a liquid, a dark border line is observed at the borders of the object. Many objects are surrounded by a narrow band of illumination, when immersed during a liquid. This band is named "becke line ". Thus, beckeline is a contrast, which outlines the transparent irregular particles, immersed in a liquid of different refractive index. This halo disappears when the liquid medium and glass have the same refractive index.

Thus, when glass particles are immersed in a liquid medium, the beckelines are appear due to the difference in the refractive indices of the glass and liquid. When the indices are equal, the becke line will disappear and this point is known as match point.

Beckeline not only indicates a difference between the indices of the glass and liquid, but also indicates which posses higher value.

c. REFRACTIVE INDEX USING HOT STAGE MICROSCOPE

The refractive index of glass can be determined by varying the temperature of immersion fluid using a special apparatus known as "hot stage".

1. The glass particle to be examined is mounted in silicone oil on the microscopic slide on the hot stage.

2. The stage is illuminated with a monochromatic source and the glass fragment is brought into focus and edge is selected.

3. The hot stage provides a stable heating and cooling. The rate of change of RI of glass with respect to temperature is app. 0.00001 per degree Celsius.

4. As the temperature of the hot stage is varied, constant observation is made to see the point, where the edge contrast is at minimum and this temperature is known as "match temperature". It is the temperature at which glass and oil will have the same refractive index.

ELEMENTAL ANALYSIS OF GLASS

In examination of glass the analysis of elements present in the glass fragment can help in determining the chemical composition of the glass fragment and can help to identify the source of the fragment. Element composition may be used to differentiate among glass made by different manufacturer or glasses from different product of the same manufacturer. A number of efforts have been made in examination of glass include various analytical techniques such as emission spectrography, neutron activation analysis (NAA), mass spectrography, inductively coupled plasma mass spectrometry (ICP/MS), scanning electron microscope, x-ray diffraction, x-ray fluorescence, Raman and infra-red spectroscopy.

The trace and minor elements present in glass samples namely, Aluminum (Al), iron (Fe), strontium (Sr), titanium (Ti), arsenic (As), lead (Pb) etc. These elements may be deliberately added in small amounts or may be present as accidental traces in the raw material. This type of qualitative analysis for the studies of the trace elements leads to a definite conclusion in examination of glass.

for more updates, subscribe to our blog.

# data[].attributes.attachment_link.title
EXAMINATION OF GLASS EVIDENCE - Modern forensic

# data[].attributes.attachment_link.description
Glass is a hard, brittle, amorphous substance obtained by fusing a mixture of silica and two or more alkaline bases, such as soda, lime or potash. It is also contains certain amount of various other elements and metals as impurities or may have been added for obtaining color, degree of hardness, heat resistance glass etc.

# data[].attributes.attachment_link.readable_text
Imagine you are convicted of a crime you did not commit and sentenced to die. You are in prison for several years during an appeals process, when finally a shining hope of being released in the form of new DNA evidence comes into play. The evidence is packaged and sent to a lab to exonerate you of the crime, except the package is destroyed during transit. The evidence that could have exonerated you is now contaminated. How angry would you feel? How defeated would you be? Something that seemed so easy to prevent from happening occurs. Your good name will never be restored, and you live the rest of your life in prison all because of a defective package. This was a very real scenario for a man by the name of Nick Yarris.

Yarris tells the story of his 21 years on death row in Pennsylvania in the documentary film, "The Fear of 13" on Netflix. One of the low points of his story was the mispackaged DNA evidence that had the potential of exonerating him of murder ten years into his sentence. Because of issues like this, it is important to educate evidence managers on proper packaging techniques used for shipping DNA Specimens to test labs. This article will serve as a general guideline for proper forensic packaging and highlight acceptable practices.
Guidelines for Packaging Evidence Solid Packaging Firearms, knives, sharp objects, and glass
These items should be placed in a sealable plastic evidence bag. The bagged article should be placed inside a rigid corrugated container. Bubble wrap should be placed inside to fill the empty container space to prevent excessive movement.

If packaging a Firearm; always ship unloaded.

Bullets, shells and clips should be shipped in a separate container.

If packaging Glass; place in a sealed rigid paperfold. It should be labeled, place inside of a hard plastic pill box. Larger pieces of glass should be thoroughly wrapped in bubble wrap and placed in a rigid container.

Liquid Packaging Blood, urine, semen, and saliva
There are four levels of packaging that must be utilized when shipping liquids: A primary watertight container, watertight secondary container, absorbent material surrounding both the primary and secondary levels and finally a rigid over box sealed with three inch pressure sensitive tape. Primary containers, made of metal, glass, and plastic, must be watertight and leak proof. Secondary containers include sealed plastic bags and varying canisters. Absorbent materials, such as cotton balls and paper towels, should be inside the secondary watertight containers surrounding the primary container and additionally surrounding the outside of the secondary container. Finally, a rigid plywood box is the preferred outer packaging. However, if a sample needs to be kept cool, a lockable rigid cooler is the suggested form of outer packaging.

However, there are restrictions for all samples that are to be shipped. These restrictions include:

Never Freeze blood samples; however, they may be placed in refrigeration if necessary.

No more than a one Liter of liquid should be shipped.

For Explosives, consult the Explosives Safety Checklist

Shipping
Make sure Proper warning labels, Biological Hazard, Dangerous Good or Hazmat information is displayed on the outside of the box. Check with your parcel carrier for information (I.e. FedEx, UPS, or USPS). Personal delivery is always the preferred method of delivery. All items that are flammable or chemically hazardous are required to be hand delivered to prevent mishandling or loss.
Final Thoughts
These guidelines can help prevent test items from being improperly packaged or damaged during transit. If proper packaged forensic samples can save the life of one individual, it is worth taking the extra steps to do it correctly.
References "Guidance for Collection, Transport and Submission of Specimens for Ebola Virus Testing." Centers for Disease Control and Prevention. Centers for Disease Control and Prevention, 05 Feb. 2015. Web. 25 July 2016. http://www.cdc.gov/vhf/ebola/healthcare-us/laboratories/specimens.html "Fedex.com Packaging Guidelines for Clinical Samples." Packaging Guidelines for Clinical Samples (n.d.): n. pag. Web, 2009. http://www.fedex.com/us/packaging/guides/Clinical_fxcom.pdf "Pointers on Shipping: Clinical Samples, Biological Substance Category B (UN 3373) and Environmental Test Samples." Clinical Samples, Biological Substance Category B (UN 3373) and Environmental Test Samples At FedEx, We Understand the Importance of Ensuring (2007): 1-6. Web.http://www.fedex.com/downloads/shared/packagingtips/pointers.pdf "Evidence Shipping Guidelines." Georgia Bureau of Investigation Division of Forensic Sciences. N.p., n.d. Web. 25 July 2016. http://dofs.gbi.georgia.gov/evidence-shipping-guidelines "Forensic Services Guide Washington State Patrol Forensic Laboratory Services Bureau." (2015): 1-113.Http://www.wsp.wa.gov/forensics/docs/bureau/forensic_services_guide.pdf. Washington State Patrol Forensic Laboratory Services Bureau. Web. Http://www.wsp.wa.gov/forensics/docs/bureau/forensic_services_guide.pdf. Washington State Patrol Crime Laboratory Division Explosive Safety and Evidence Checklist: http://www.wsp.wa.gov/forensics/docs/crimelab/safety_checklist.pdf Riley, C. (Producer), & Sington, D. (Director). (2015). The Fear of 13 [Documentary]. United Kindom: Dogwoof. (NetFlix)

# data[].attributes.attachment_link.title
Proper Packaging for Forensic Evidence Can Save Innocent Lives

# data[].attributes.attachment_link.description
Imagine you are convicted of a crime you did not commit and sentenced to die. You are in prison for several years during an appeals process, when finally a shining hope of being released in the form of new DNA evidence comes into play.