development of a for the differentiation of gsr - quodata · 2013-10-19 · technische universitÄt...

TECHNISCHE UNIVERSITÄT BERGAKADEMIE FREIBERG

Sylvia Steffen,Institute for Analytical Chemistry ENFSI XIII. Meeting, Firearms Working Group, Copenhagen, 31st May – 02nd June 2006 1

"Development of a "Development of a for the Differentiation of GSR"for the Differentiation of GSR"

-- Status Quo Status Quo --

EUEU--Project No.: Project No.: JLS/2005/AGIS/031JLS/2005/AGIS/031(former project: (former project: JAI/2003/AGIS/033JAI/2003/AGIS/033))



OverviewOverview

1. Project Aim

2. Summary of Results from project JAI/2005/AGIS/033:Chemometric Assessment of SEM/EDX Data by RDA (Regularised Discriminant Analysis)

3.

4. Outlook, Future Work



OverviewOverview

1. Project Aim


3.




1. Project Aim1. Project Aim

Project JAI/2003/AGIS/033: "Statistical Evaluation of Particle Analysis by SEM/EDX for the Differentiation ofGunshot Residues (GSR)"

• Chemometric assessment of EDX-spectral data (elemental composition -qualitatively and quantitatively)

• Chemometric assessment of additional particle data (e.g. morphology)

• Regularised discriminant analysis and multivariate regression analysis to establish a model for differentiation / classification

Project JLS/2005/AGIS/031: "Development of a 'GSR Browser' for the Differentiation of GSR"

• Programming of a 'GSR Browser' containing all relevant information to allow a faster approach in casework

Regularised discriminant analysis



OverviewOverview

1. Project Aim


3.




2. 2. ChemometricChemometric AssessmentAssessment

Regularised Discriminant Analysis (RDA)

Confusion matrix for the classification of unknown particles (sample matrix) into the model (training matrix) for the Pb-containing primers;training matrix: 3000 particles, sample matrix: 1000 particles, λ = 0.9, γ = 0, risk of misclassification: 9.0%

1 Geco Sinoxid (DNAG) - PbSbBa2 Fiocchi - PbSbBa3 Samson TZZ (IMI) - PbBaSbCa4 Hirtenberger HP - PbBaSiCa5 Lapua - PbBaSiCa6 S & B Neroxin - PbBaSiCa7 Winchester Western - PbSbBa8 Amer. Eagle (Federal) - PbSbBa

12

34

56

78

12

34

56

78

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

"True" ammunition"Assigned" ammunition

Rel

ativ

e nu

mbe

r of a

ssig

ned

parti

cles

[%]

82%

67%

51%

76% 71% 69%

83% 86%




Regularised Discriminant Analysis (RDA)

Confusion matrix for the classification of unknown particles (sample matrix) into the model (training matrix) for the Pb-free primers;training matrix: 3000 particles, sample matrix: 1000 particles, λ = 0.5, γ = 0, risk of misclassification: 2.1%

1 S & B NonTox - SiKCa2 Fiocchi Leadless - SbBa3 Magtech Clean Range) - Sr, 30%4 Sintox, Cu-jack. (DNAG) - ZnTi(CuZn)5 Sintox, Sn-jack. (DNAG - ZnTi(Sn)6 CCI Blazer - Sr, 30%7 Winch. West. "Super-X" - K, 20% 1 2 3 4 5 6 7

12

34

56

7

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

"True" ammunition

"Assigned" ammunition

Rel

ativ

e nu

mbe

r of a

ssig

ned

parti

cles

[%] 90% 93%

100% 92% 92% 93% 97%



Confusion matrix for the classification of unknown particles (sample matrix) into the model (training matrix) for the combined matrix (Pb-containing and Pb-free primers); training matrix: 3000 particles, sample matrix: 1000 particles, λ = 0.5, γ = 0, risk of misclassification: 7.6%


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

"True" ammunition

"Assigned" ammunition

Rel

ativ

e nu

mbe

r of a

ssig

ned

parti

cles

[%]

79%

66%

34%

70% 66%

54%

85% 81% 80%

94% 85%

83% 90%

94% 97%



OverviewOverview

1. Project Aim


3.




3. 3. 1. Set preferences



2. Load appropriate model• Pb-containing• Pb-free• combined

3. Load samples(spectra from SEM-run)

3. 3.



4. Calculate

3. 3.



Plot types:

• Global view: bar-chart to illustrate class assignment• Individual match: dots for assignment of individual particles within the examined sample• Individual details: colour-scheme (qualitatively) for class assignment based on discriminant rules• Individual Mahalanobis:

colour-scheme (semi-quantitatively) to illustrate distances to class centroidsbetween and within classes

• Individual class summary:modified 'compass' plot to choose the correct model for classification(based on min/max borders and symmetry)

3. 3.



5. Global view – bar-chart

3. 3.



6. Individual match – dots

3. 3.



7. Individual details –colour-scheme

- based on discriminantrules

- purely qualitatively(one spectrum is assign-ed to class with highestprobability)

3. 3.



8. Individual Mahalanobis –colour-scheme

- based on 'MahalanobisDistance' as measure to class centroid

- semi-quantitatively(one spectrum is assign-ed to all classes with its distance measure)

- compare 'best fit' and compa-re different spectra relative toeach other

3. 3.



9. Individ. Class Summary, based on inverse Mahala-nobis – 'compass' plot

- based on inv. 'MahalanobisDistance' as measure to class centroid

- defining min. and max.values (in terms of borders)

- decision whether chosen model is correct – compareborders, assess symmetry ofpolygon

Correct model'Wrong' model

3. 3.



10. Choose models and samples input

3. 3.



Features:

+ zooming-in+ zooming-out+ switching between models and samples+ switching between plot types

Assessment:

- Correct model ???Mahalanobis plots: correct model shows 'class', wrong model has similar probabilities for all classes

- Assignment of 'unknown' particles

3. 3.



4. Outlook, Future Work4. Outlook, Future Work

Planned WorkPlanned Work:

• Collect and include more data

• Further chemometric assessments (morphology, other chemometric tools)

• Optimisation of

• Program data-export function for report generation

• . offered to all European forensic institutes performing GSR investigation

• Testing of in casework



AcknowledgmentsAcknowledgments

• Dr. Ludwig Niewöhner (BKA-KT23), Dr. Martin Barth (BKA-KT23)

• Prof. Dr. Matthias Otto (TU Freiberg), Mr. Björn Knauthe (TU Freiberg)

• The project partners:– IES (Poland): Dr. Zuzanna Brózek-Mucha– KEÚ PZ (Slovakia): Dr. Ronald Horvath– NFI (Netherlands): Dr. Amalia Brouwer-Stamouli– NICC (Belgium): Dr. Bart Nys

• The European Union (EU)



Correct model:'Wrong' model:

development of a for the differentiation of gsr - quodata · 2013-10-19 · technische universitÄt...

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