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A Forensic Scientist examining broken glass at a crime scene GClark

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A scientist is collecting a piece of glass from a crime scene for evidence.
A.Alston

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CARVETTA HARDEN

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Police searched for a vehicle that had the same damage as the hit and run car. Then they found a car with those damages that belonged to Susan Nutt. In order to connect Susan's car to the glass fragments found at the crime scene to the glass on her car, refractive index tests needed to be done. This job was done by researchers at Oregon State University's Radiation Center. The scientists there found that the windshield glass contained the same 22 chemicals as the ones in Susan's car. They also said that both samples of glass were a definite match.

The glass evidence helped convict Susan Nutt. She failed to preform duties of a driver for an injured person. She was sentenced to 5 years in jail.

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On a dark, cloudy night in February, at 9:30 pm, a 19-year-old named Craig Elliott Kalani went for a walk with his dog in his neighborhood but he never returned because a hit and run driver killed...

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something cardboard works good
A.Alston

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CARVETTA HARDEN

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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).

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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).

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CARVETTA HARDEN

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Always have gloves no matter what and photograph
A.Alston

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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).

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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).

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Glass standards for refractive index measurements- A.Alston

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ATF Trace Evidence Unit Reference Collections

Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF)

Collections of various trace evidence samples; automotive paint pigments, human hair, animal hair, fibers, black spray paint, silicone adhesive, electrical tape, and duct tape. Collections include various automotive paint pigments, human hair, animal hair, fibers (hundreds), black spray paints (~10), silicone adhesives (30-50), electrical tape (30-40), and duct tape (20-30).

Collection can be accessed by emailing POC.

Some samples (i.e. human and animal hair) are steadily accumulated. Others (i.e. black spray paint, silicone adhesives) are collected for a specific case. Samples are collected from various sources, including volunteers, casework, and commercial vendors.

Physical samples.

Leonora Bender
Bureau of Alcohol, Tobacco, Firearms,
and Explosives (ATF)
202.648.6146

Digital Automotive Image System (DAIS)

Automobile Identification

Federal Bureau of Investigations (FBI) -- Digital Evidence Laboratory

A digital system, which fits entirely on one DVD, with photos and data of motor vehicles commercially manufactured in the last twenty years. Used in image analysis to provide opinions as to whether a car in a photo could be a particular make, model, or year car. Collection of images of make, model and year of cars. Includes front, side, and rear photos of motor vehicles and accompanying data. The software can generate "Be On the Lookout"-type posters and produce photo lineups. DAIS contains thousands of records.

User must request a DVD from the FBI. Database can then be downloaded from DVD and installed on an unlimited number of computers. The data is searchable by vehicle category, body style, number of doors, and other characteristics. CDs are available up request to law enforcement only.

Images are obtained per contract with Southwest Research Institute through TSWG.

Digital records.

EPA NEIC Asbestos Collection

Asbestos, Silicate Mineral

Private Collection, Owner works for EPA NEIC

Self-maintained, private collection of asbestos samples. Owner is willing and has provided samples to requesting parties on occasion. The collection contains 20-40 asbestos samples collected from mines in North America (Vermont, Quebec, North Carolina, Arizona), rockshops, and bookshops.

Contact the POC/Owner. Physical samples are available for some, but not all, of the collection's specimens. Currently only used internally and for educational purposes in court. Any outsider with a legetimate cause can request access.

Samples collected from caves, or purchases in rockshops and bookshops by the collection owner.

Physical samples.

Peggy Forney,
Collection Owner
National Enforcement
Investigations Center,
EPAC
Chemist
303.462.9110

European Collection of Automotive Paints (EUCAP)

Paint, Automobile Identification

The French Police Lab maintains the database; data analysis is performed by the Federal Criminal Police Force of Germany (BKA).

A searchable collection of paint samples removed from primarily salvage vehicles by law enforcement laboratory participants throughout Europe. Paint samples collected by European Law Enforcement Agencies.

The database can be accessed via the internet via a secure ID and password assigned by the French Police Lab.

FBI Lab - Fiber Library

Fibers

Federal Bureau of Investigations (FBI) -- FBI Laboratory

Database of FTIR spectra of textile fibers used to identify fiber types. Database includes 86 records. Each record includes FTIR spectra. Physical samples of fibers are also held.

Library is stored in FBI's version of the OMNIC library search software (Thermo Fisher Scientific Inc.). Outside agencies can request FBI Trace Evidence staff to carry out analysis by contacting POC. No cost to access; outside labs and agencies can submit requests to FBI.

Most of the fiber samples were obtained from Collaborative Testing Services (a commercial company).

Digital records and physical samples.

FBI Lab - Forensic Automobile Carpet Database (FACD)

Fibers, Automobile Identification

Federal Bureau of Investigations (FBI) -- FBI Laboratory

A collection of carpet fibers removed from vehicles. Fibers are entered into a centralized searchable database that is used to provide investigative make/model/year information. Collection includes about 800 samples of known automobile carpet fibers. Records include microscopic characteristics including cross-section, diameter, color as seen through microscope, IR microscopy, microspectrometry.

Sample is first analyzed and a search is carried out using a Microsoft Access database. The sample is then compared with physical samples of possible matches. Outside law enforcement agencies will be able to submit evidence for analysis by the FBI. No cost to access; outside labs and agencies can submit requests to FBI.

Fibers come from personally-owned vehicles, manufactures, and junkyards.

Digital records and physical samples.

Stephen Shaw
Federal Bureau
of Investigations,
FBI Laboratory
703.632.7706 stephen.shaw@
ic.fbi.gov

International Forensic Automotive Paint Data Query (PDQ)

Paint, Automobile Identification

Royal Canadian Mounted Police (RCMP)-- Forensic Laboratory Services

The International Forensic Automotive Paint Data Query (PDQ) database is a centralized, searchable database of chemical and color information of original automotive paints. Search results provide make/model/year information. PDQ contains foreign and domestic automotive paint samples from ~13,000 vehicles and ~50,000 layers of paint. Most paint samples consist of four layers typically used for an automotive job. Contains majority of post-1973 vehicles marketed in the US.

Access is granted through a program updated and released by RCMP annually through a CD release. Law enforcement agencies interested in PDQ who are not already members can contact PDQ directly by email. Partnering agencies also have access to physical samples by request. Use of the PDQ is for bona fide law enforcement agencies only that perform forensic paint examinations as part of criminal investigations. "Payment" for access to the database is the submission of 60 samples to PDQ each year. In addition, users must sign a non-disclosure agreement.

Every accessing institution must submit 60 paint samples per year, these usually come from vehicles at body shops or junk yards or manufacturers. Samples are also collected directly from some automotive companies.

Samples are analyzed for their identifying chemical properties, and this information is stored digitally. Physical samples are available by request (see more information).

Email PDQ:

Mark Sandercock
Manager, Trace Evidence
Operations Support
National Centre for
Forensic Services -
AlbertaRoyal Canadian
Mounted Police
780.451.7418
mark.
sandercock@
rcmp-grc.gc.ca

Diana Wright
Federal Bureau
of Investigations,
FBI Laboratory
703.632.7418

Locke Scientific - GRIM Glass Standards

Glass

Locke Scientific (commercial)

Glass standards for GRIM.

Standards can be purchased for use in the laboratory.

Physical samples.

Susan Gross
Minnesota BCA
Chemistry Supervisor
651.793.2900
sue.t.gross@
state.mn.us

McCrone Microscopes & Accessories - Slide Sets

Reference Materials/ Standards

McCrone Microscopes & Accessories (commercial)

Microscope company stocks a number of slide sets that serve as reference collections for forensic analysis. Sets include a paint pigment set, particle set, fiber reference sets, white powder set, and an asbestos reference set. Paint Pigment Set - 50 samplesFiber Reference Set - 100 samplesAsbestos Reference Set - 25 samples; includes materials that contain asbestosParticle Reference Set - 100 samplesWhite Powder Set - 25 samples

Standard reference materials and slide sets can be searched and purchased on the website. Paint Pigment Set - $325.00; Fiber Reference Set - $725.00; Asbestos Reference Set - $450.00; Particle Reference Set - $725.00; White Powder Set - $300.00

Samples in each slide set are selected by based on most commonly seen specimen for each category.

Physical samples purchased from an online catalogue.

MicroTrace - SRM Collections

Reference Materials/ Standards

MicroTrace Scientific (commercial)

Company that sells reference material collections and slide sets. Reference materials include forensic fiber reference collection, natural fiber collection, hair and fur collection, forensic mineral analysis slide set, and automotive pigment reference collection. Reference Collections- Fiber Reference Collection: 200 traceable, authenticated synthetic fibers- The Arbidar Animal Hair and Fur Collection: 80 animal hair samples from around the world representing 49 genera- The Arbidar Natural Fiber Collection:80 samples representing a wide variety of natural fibers including vegetable fibers, animal fur fibers used in textiles, silks, and papersSlide Reference Collections:- Forensic Mineral Reference Collection: approximately 40 slides of minerals that are forensically significant- Automotive Pigment Reference Collection: approximately 40 slides of paint pigments from automotive manufacturers

Standard reference materials can be searched and purchased on the website. Cost varies by product; legitimate forensic laboratories can purchase.

N/A

Physical samples are available for purchase through the online catalog.

Microtrace LLC
790 Fletcher Drive
Suite 106
Elgin, IL 60123-4755
847.742.9909

National Automotive Paint File (NAPF)

Paint, Automobile Identification

Federal Bureau of Investigations (FBI) -- FBI Laboratory

A physical collection of automotive paint panels acquired and maintained by the FBI's Chemistry Unit for use in casework. NAPF is a physical collection of paint color standards and/or full system paint panels (as a vehicle would be painted, not just the top coats). It contains approximately 14,000 automotive paint panels.

NAPF is used in an investigation to make a physical comparison of evidentiary paint chips to known paint colors to aid in identifying possible vehicle makes and models in hit-and-run investigations. The FBI Lab may be able to provide small samples of specific vehicle colors to other law enforcement agencies if that agency has some knowledge of the specific color or model they are seeking.

Automotive manufacturers provide these physical samples free of charge to the FBI Lab for all vehicles available for purchase in North America. This does not include commercial vehicles such as trucks, buses, motorcycles or RVs.

NAPF is not a database; physical samples are available.

Diana Wright
Federal Bureau
of Investigations,
FBI Laboratory
703.632.7418

National Forensic Tape File (NFTF)

Tape

Federal Bureau of Investigations (FBI) -- FBI Laboratory

The National Forensic Tape File is used for determining the manufacturer and/or product for duct tape sourcing requests and is also a repository for samples used in the FBI duct tape and electrical tape discrimination studies. ~500 tape samples stored in-house in plastic bags and plastic bins in a storage cabinet. Physical properties and/or chemical composition can be searched in SLICE software to determine potential manufacturer/product candidates, and then those candidates can be pulled out of NFTF for a direct comparison to the unknown sample.

The Florida Department of Law Enforcement (FDLE) and FBI both use SLICE software to interact with digital tape records. - FDLE and FBI are willing to share their digital records with other forensic scientists that have SLICE and are willing to share/exchange samples.- For a laboratory without the SLICE software, the FBI can conduct the analysis for them as long as it adheres to the case acceptance policy. Case Acceptance Policy: Usually if it's a case that has FBI jurisdiction, they will accept it and perform the analysis. If the lab has its own capabilities, then it must do the analysis itself (but FBI and FDLE will share/exchange data and samples).

Manufacturers provide rolls free of charge (majority of samples) or samples are purchased. A new roll is assigned a sequential number, put into a storage cabinet, its paperwork is filed, and then it is analyzed and data is put into SLICE.

Digital records can be shared through the SLICE software. Physical samples are maintained in-house.

Andria Mehltretter
Federal Bureau
of Investigations,
FBI Laboratory
703.632.7415
andria.
mehltretter@
ic.fbi.gov

Polyethylene Repository & Information Database for Evdience (PRIDE)

Plastic Bags

Federal Bureau of Investigations (FBI) -- FBI Laboratory

Repository of polyethylene reference samples. Examples include trash bags and sandwich bags. Database can be used to determine the possible manufacturer of a bag used at a crime scene. Collection includes approximately 1,000 samples of polyethylene bags.

There is a standalone system at the FBI Laboratory Questioned Documents Unit. The QDU will search the system to fulfill outside requests. Outside agencies submit the questioned specimen for QDU to do analysis. No cost to access; outside law enforcement agencies can submit requests to the FBI.

Samples were obtained as part of a research project for development of the database. Additional samples are provided by the program manager. Submitted samples are not added to PRIDE because manufacturer information is unknown.

Digital records and physical samples.

Meg McHenrymarguerite.mchenry [at] ic.fbi.gov (marguerite.
Federal Bureau
of Investigations,
FBI Laboratory
703.632.7283

mchenry@
ic.fbi.gov)

Contacts if agencies have questions:

FBI Questioned
Documents Unit:
703.632.8444

FBI Evidence Control: 703.632.8360

Powder Diffraction File (PDF)

Powders

International Center for Diffraction Data (ICDD)

Database of powder diffraction data for the identification of crystalline materials. The database can be purchased in different versions. Collection includes 715,953 total records, broken down into numerous libraries that the user can purchase depending on user needs (basic version, advanced version, and mineral and organics add-ons). Diffraction, crystallographic, and bibliographic data are kept on each data set. Select physical properties are also kept.

PDF can be purchased as a standalone version on user's PC (depending on version). User must first purchase a license (1 year for advanced version, 5 years for basic version). For sales information, call the number listed or visit the website. Pricing information for various packages appears on the brochure. Product may be purchased after agreeing to the licensing terms.

The following institutions are collaborative partners on PDF:- International Center for Diffraction Data (ICDD); Newtown Square, PA- Cambridge Crystallographic Data Centre (CCDC); Cambridge, UK, Cambridge Structural Database (CSD)- National Institute of Standards and Technology (NIST); Gaithersburg, MD- Fachinformationszentrum Karlsruhe (FIZ); Karlsruhe, Germany, Crystal Structure Database (ICSD)- Material Phases Data System (MPDS); Vitznau, Switzerland, Linus Pauling File (LPF)

Digital records.

TireGuides, Inc. - Tread Design Guide

Impressions

Tire Guides, Inc. (commercial)

Database of tire tread designs utilized to provide investigative lead information on possible make and model for unknown impressions. The Tread Design Guide shows tread patterns for all types of tires sold in the U.S.*A comprehensive Visual Identification of all types of Tire Tread Pattern Designs.*Covers Passenger, Light Truck and Medium Truck vehicles.*Includes Off-Road and Agricultural Tread Patterns.*Also covers Motorcycle and retread tire tread designs.*Provides information on how to read a tire sidewall and on the different Tire Sizing Systems.*Gives detailed information on Speed-Rating and Load Indexes as well as lug nut torque and tightening sequences.*Back Issues available.

The individual guides can be purchased as a hardcopy book. A computerized version is also available. Contact Tire Guides Inc. by phone or through the URL. Price Quantity (from website)$28.00 1 - 4 $27.00 5 - 9 $25.00 10 - 24 $24.00 25 - 99

Tread patterns and other information compiled for tires sold in the U.S..

Digital records.

Tire Guides Inc. -
Tire Information Center
1101 South Rogers Circle
Ste 6
Boca Raton, FL 33487-2748 561.997.9229
tireinfo@
tireguides.com

TSWG Sponsored FIU Glass Database

Glass, Elemental Analysis

Florida International University, sponsored by the Technical Support Working Group

The database assesses the relative frequency that two glass samples from different sources would have the same elemental profile. The purpose of this database is to provide glass examiners a view of the frequency of occurrence of elemental composition for ~700 different glass samples originating from different sources. The database contains elemental analysis data for 12 elements for ~ 700 glass samples from manufacturers, distributors, and vehicle junkyards. Samples include: containers, float, headlamp, and vehicle glasses.

The database is not designed to be searched for casework in the way that other forensic databases (i.e. PDQ) but rather, it is to be used by researchers to estimate the probability of a random occurrence of elemental composition for different glass sources. Two plasma mass spectrometers are used to perform an elemental analysis of glass. Freely available to agencies and researchers with a reasonable cause.

Samples are collected from manufacturers, distributors, and vehicle junkyards. The data was collected from a single laboratory (FIU) as part of a research project.

Digital data records.

Dr. Jose Almirall, Professor
Department of Chemistry
and Biochemistry,
Florida International
University
305.348.3917

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ATF Trace Evidence Unit Reference Collections Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) Collections of various trace evidence samples; automotive paint pigments, human hair, animal hair, fibers, black spray paint, silicone adhesive, electrical tape, and duct tape.

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put glass in cheeseburger- A.Alston

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Crime Scene

The police officer, recalling that night, sounds like an actor in a fast-food commercial: "At some point, something told me, grab a Big Mac." And so on a freezing January night in 2005, the officer, John Florio, then 39, stopped at the drive-through window of a McDonald's in the Hunts Point section of the Bronx. He ordered the combo, a Big Mac with fries and a Coke.

"Have a nice night," a young man in the cashier's window said, according to Officer Florio.

"You, too," the officer replied.

He drove away, with his dog, Dodger, a member of the Police Department's canine unit, in the back seat. Officer Florio was heading toward Randalls Island to give Dodger a bathroom break and a run. As he drove, he bit into the burger. Top-row teeth met bottom-row teeth, and the course of two lives changed.

"I felt something hard and sharp on the left-hand side of my face," he said on a witness stand five years later. Something had cracked: "My tooth."

Inside the Big Mac were several shards of broken glass.

It is impossible to overstate the seriousness with which the police take any attempt to harm one of their own. To the passer-by that night, it must have looked as if an officer had been drawn and quartered in the McDonald's: there were two inspectors, two captains, three sergeants and five detectives among other officers at 875 Garrison Avenue.

They combed the kitchen for glass and questioned employees and a manager, and they took the young man assembling sandwiches that night, Albert Garcia, then 18, into a back room, where he was questioned for about three hours. He confessed.

"I started to make the sandwich and I was about to finish it," he wrote in a statement for detectives. "I put the little pieces of glass into the burger as a joke." He wrote, "I didn't know it was going to be sold to a cop."

Then the case that seemed so open and shut just kept opening.

Five years passed before Mr. Garcia's trial began in the Bronx, and by then he had not only renounced his confession, but his lawyer, Raymond J. Aab, had accused Officer Florio of planting the glass in his own burger to make a quick buck from McDonald's.

The officer guessed that he bought the Big Mac around 11:30 that Saturday night, Jan. 29, 2005, but he had no receipt. He said Mr. Garcia had handed him the bag. He bit into the glass a couple of minutes later, he testified, but he did not call his sergeant until 12:07 a.m., after stopping at Randalls Island for his dog. He followed the sergeant's command to get checked out at Long Island Jewish Medical Center, and he told doctors that he thought he had swallowed glass.

Image

An evidence photo shows a McDonald's Big Mac and bits of glass that Officer John Florio said were in the burger when he bought it in January 2005.

One doctor said, five months later, that he had had three foreign-objects-in-McDonald's-food cases that week, all from different locations. Doctors found no sign of cuts to Officer Florio's throat, and X-ray tests came back negative. But Officer Florio said he monitored his stool for several days after, going to the bathroom in a bucket and examining its contents, and he found five shards of glass that had apparently passed through him without causing injury.

Inside of two weeks, Officer Florio sued McDonald's for $6 million. This would prove to be a tactical mistake, for the civil action allowed the defense team to question him and other police officers in depositions, a luxury unknown to most lawyers defending criminal cases. The depositions contradicted one another in various places, and a defense theory emerged: Officer Florio planted the glass and never laid eyes on Mr. Garcia that night; nor did Mr. Garcia see the officer. The cashier, a young woman, served him the burger.

But when detectives, believing Officer Florio's story, interviewed Mr. Garcia and he appeared nervous, they pushed harder, and he confessed.

Officer Florio, the defense claimed, had learned of Mr. Garcia's existence only many hours later, in a precinct station house, and, quite likely shocked that anyone had confessed to something that did not happen, said yes, that's the guy.

The defense theory worked. A jury acquitted Mr. Garcia in March 2010.

Officer Florio, since retired, settled his lawsuit against the owners of that Bronx franchise restaurant for $15,000, his lawyer, Richard M. Kenny, said. It was a fraction of what he had sought.

Officer Florio declined to comment, but Mr. Kenny said: "I've kicked a lot of people out of my office who I believe are trying to perpetrate fraud. This guy is as legitimate a guy as I've ever met."

Mr. Garcia said that he had gone on, improbably, to work at a White Castle restaurant a few months after his arrest, and that his new employer did not know it had hired "Burger Boy," as people in Hunts Point called him. He now works for Walgreens, has two children, and has a lawsuit pending against the city and Officer Florio. A scheduling conference in that case is set for next month.

"The reason I made a false confession is because I was scared," he said this week. "I've never been in that type of position before. I gave up mentally. I was exhausted. I was hungry. I was thirsty. The only thing I was thinking about was going home."

A police spokesman, Paul J. Browne, shrugged off Mr. Garcia's lawsuit.

"It's no surprise that the plaintiffs' bar seeks remuneration for clients, regardless of how dubious their claims," he said.

The Big Mac remains in evidence six years later, in a city freezer. The case of the broken glass is not even its only mystery. Investigators found a strand of hair in the burger box, but forensic tests showed that it belonged to neither the young man who was accused in the case nor the officer who paid for a meal and drove away.

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Tale of Glass in Burger Lingers (Published 2011)

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Crime Scene The police officer, recalling that night, sounds like an actor in a fast-food commercial: "At some point, something told me, grab a Big Mac." And so on a freezing January night in 2005, the officer, John Florio, then 39, stopped at the drive-through window of a McDonald's in the Hunts Point section of the Bronx.

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CARVETTA HARDEN

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CARVETTA HARDEN

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CARVETTA HARDEN

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Forensics: Glass Fragment Analysis

Description:

Glass as a physical clue is frequently encountered in crimes such as burglary, murder, road accidents, and vandalism. The examination of glass evidence has depended, traditionally, on comparing the physical and chemical characteristics of a questioned fragment with a known fragment. The physical measurements include the observation of colour, thickness, density, and optical properties. Normally, the prosecution will try to show that the crime scene evidence and that recovered from a suspect have the same source, the defence will try to show they have different sources. If the suspect was at the crime scene then the fragments found on him could have come from the window at the crime scene, if he was not there then the fragments have come from some other, unknown, source.

Recent advances in analytical capabilities for the trace element characterisation of glass fragments have provided a high degree of discrimination between glass fragments that was previously not available with the physical property comparisons. Work currently being carried out in the Advanced Reasoning group has focussed primarily on the statistical modelling of the variation in such measurements - variation within a glass fragment and variation between fragments from different sources. The classification of glass samples into their product-use type is also important; for example in corroborating or disproving an alibi or product tampering. It is possible to differentiate between various types of glass (such as headlamp glass, container glass, non-vehicle window glass etc) using knowledge of the concentration of its constituant elements and optical properties.

The aim of this project is to investigate the utility of several machine learning methods for the task of glass sample classification. Given an unknown glass sample, the resulting system should be able to determine its type by its chemical make-up. A real-world glass fragment dataset has been obtained and will be made available. It is expected that not all features involved (in this case, chemicals) will be useful for determining glass type, and hence feature selection methods should also be applied.

References:

C.G.G. Aitken. Statistical Interpretation of Evidence/Bayesian Analysis, Encyclopedia of Forensic Sciences, Academic Press, pages 717-724, 2000.

R. Jensen and Q. Shen. Semantics-Preserving Dimensionality Reduction: Rough and Fuzzy-Rough Based Approaches. IEEE Transactions on Knowledge and Data Engineering, 16(12): 1457-1471. 2004.

T. Mitchell. Machine Learning,, McGraw Hill, 1997.

Back to project index

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Forensics: Glass Fragment Analysis Description: Glass as a physical clue is frequently encountered in crimes such as burglary, murder, road accidents, and vandalism. The examination of glass evidence has depended, traditionally, on comparing the physical and chemical characteristics of a questioned fragment with a known fragment.

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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).

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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).

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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.

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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.