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Forensics

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A team of 2 students competes for 50 minutes to analyze crime ... Lavender Purple. Orange. Red. Yellow. Yellow, Burned. Add NaOH. NaCl, Glucose, Sucrose. MgSO4 ... – PowerPoint PPT presentation

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Title: Forensics


1
Forensics
  • Division C

2
  • Andy Shaw
  • Sr. Research Biochemist
  • Merck Co.
  • West Point, PA
  • Ph.D. in Chemistry
  • University of Illinois
  • 7 years involvement with Science Olympiad
  • 5 years State Event Supervisor
  • 3 years Regional Event Supervisor
  • 2005 National Event Supervisor
  • 2006 Coaches Clinic Presenter

3
Event Parameters
  • A team of 2 students competes for 50 minutes to
    analyze crime scene evidence and write a summary
    of their analysis
  • Scoring
  • Analysis of evidence 70.
  • 4 parts 15 20 each
  • Written summary of the analysis 30.

4
Rule Changes
  • Students may bring an 8½ x 11 paper with
    handwritten notes on BOTH sides
  • Changes in the number of parts of the event and
    samples with those parts
  • IR and UV/Vis spectroscopy removed
  • Students are expected to know how DNA is copied
    (PCR) and be able to compare electropherograms
  • Changes in blood analysis and bullet analysis

5
General Safety Precautions
  • Safety! Safety! Safety! Safety! Safety!
  • Bring and wear lab coat/apron that cover the
    knees, OSHA approved indirectly vented splash
    goggles (over the eyes), pants/skirt that cover
    the legs to the ankles (no shorts)
  • No open toed shoes
  • No tasting or touching chemicals

6
Student Equipment
  • Test tubes/holder
  • Droppers
  • Funnels
  • Filter paper
  • pH paper
  • Spatulas
  • Stirring rods
  • Thermometer
  • 9-Volt conductivity tester
  • Nichrome wire
  • Cobalt blue glass
  • Metal tongs
  • Slides
  • Notes
  • Calculator

7
Materials Provided
  • I2 dissolved in KI (Lugols Solution)
  • 2 M HCl
  • 2 M NaOH
  • Benedicts solution
  • Hot water bath
  • Heat source-flame testing
  • Distilled water
  • Instructions for testing simulated blood samples
  • Matches and candle for fabric burn tests
  • Solutions that can be used for density testing
    with polymers e.g. saltwater, alcohol, corn oil,
    or other similar materials

8
Unknown Powders
9
NaC2H3O2, NaCl, NaHCO3, Na2CO3, LiCl, KCl,
Ca(NO3)2, CaSO4, CaCO3, Cornstarch, Glucose,
Sucrose, MgSO4, H3BO3, NH4Cl
Add water
CaSO4, CaCO3, Cornstarch
NaC2H3O2, NaCl, NaHCO3, Na2CO3, LiCl, KCl,
Ca(NO3)2, Glucose, Sucrose, MgSO4, H3BO3, NH4Cl
Insoluble
Soluble
pH paper
Strong BaseNa2CO3
Weak BaseNaC2H3O2, NaHCO3
No ReactionNaCl, LiCl, KCl, Ca(NO3)2, MgSO4,
Glucose, Sucrose
AcidNH4Cl, H3BO3
Add NaOH
Optional
NH4Cl
H3BO3
NH3 odor
No odor
10
Add HCl
Flame test
Add HCl
CaCO3
CaSO4
Cornstarch
Bubbles
Solution above solid clarifies
Cloudy, gelatinous
NaHCO3
NaC2H3O2
Na2CO3
No reaction
Bubbles
Bubbles
KCl
Ca(NO3)2
LiCl
NaCl, MgSO4
Glucose, Sucrose
Lavender Purple
Orange
Red
Yellow
Yellow, Burned
11
Add NaOH
NaCl, Glucose, Sucrose
MgSO4
Translucent precipitate
No reaction
Add Benedicts
Glucose
NaCl, Sucrose
Orange precipitate
No reaction
Add Hot Water
NaCl
Sucrose
High solubility
Low solubility
12
Polymers
  • Densities/SP. GR.
  • 1.38
  • 0.90
  • 1.20
  • 0.95
  • 0.92
  • 1.05
  • 1.37
  • 1.16
  • Name
  • Polyvinylchloride
  • Polypropylene
  • Polycarbonate
  • High Density polyethylene
  • Low Density polyethylene
  • Polystyrene
  • Polyethyleneterephthalate
  • Polymethylmethacrylate

Values are approximate
13
Densities of Common Solvents
  • Water
  • 10 Salt Water
  • 20
  • 25
  • Saturated NaCl
  • 50 Ethanol/water
  • 70 Isopropanol
  • Mazola Oil

1.0g/ml 1.07 1.15 1.19 1.36 0.94 0.93 0.918
Source Handbook of Chemistry and Physics
14
Polymer Scheme
Unknown Polymers
floats
Add to waterSp. Gr. 1.0
Add 46 IsopropanolSp. Gr. 0.94
floats
sinks
Add to Vegetable OilSp. Gr. 0.92
floats
Add to 10 NaCl solutionSp.Gr. 1.07
sinks
PP
floats
sinks
PS
LDPE
HDPE
Contd next page
15
Add to 10 NaCl solutionSp.Gr. 1.07
sinks
Add to saturated NaClSp. Gr. 1.36
floats
Add to 25 NaCl Sp. Gr. 1.19
floats
sinks
sinks
PC
PMMA
PETE
Burn test result- yellow flame
PVC
Burn test result- green flame
16
Fiber Analysis
  • Cotton---------Burn Test and lack of odor
  • Wool----------Burn Test/odor of burning hair
  • Synthetic-----Melts

17
Paper Chromatography
  • Chromatography results may vary depending on
    solvent
  • For example, isopropanol vs. water
  • If solvent is provided, use it
  • Chromatography samples generally run slow and
    need to be run longer than students think (15-20
    minutes)

Ink samples spotted on filter paper Isopropanol
as solvent Suspects 3 6 computer ink matches
computer printout found at scene
18
Fingerprint Analysis
  • Plain Arch
  • Tented Arch
  • Radial Loop
  • Ulnar Loop
  • Central Pocket Loop
  • Double Loop
  • Whorl
  • Accidential

19
Fingerprint Analysis Definitions
  • Core center or focal point of the print
  • Bifurcate the splitting of a ridge into two
  • Delta another center or focal point of the
    fingerprint
  • Ridge count number of ridges that either cross
    or touch an imaginary line usually connecting the
    core and delta

20
Blood Typing (Serology)
  • Students are provided with simulated blood
    samples and antibodies and instructions on how to
    test the samples
  • General background information can also be
    provided, but some knowledge is assumed
  • Each blood sample has to be tested with each
    antibody to arrive at the correct answer

21
Blood Typing Background
  • The differences in human blood are due to the
    presence or absence of certain protein molecules
    called antigens and antibodies.
  • The antigens are located on the surface of the
    red blood cells and the antibodies are in the
    blood plasma.
  • Individuals have different types and combinations
    of these molecules. The blood group you belong to
    depends on the genetics you have inherited from
    your parents.
  • There are more than 20 genetically determined
    blood group systems known today, but the AB0 and
    Rh systems are the most important ones used for
    blood transfusions.
  • Not all blood groups are compatible with each
    other, as some contain antibodies for other blood
    types.
  • Mixing incompatible blood groups leads to blood
    clumping or agglutination, due to the foreign
    antibody attaching to the antigen on the surface
    of the blood cell, which is dangerous for
    individuals.

22
Blood Groups and Instructions
  • Blood group A If you belong to the blood group
    A, you have A antigens on the surface of your red
    blood cells and B antibodies in your blood
    plasma.
  • Blood group B If you belong to the blood group
    B, you have B antigens on the surface of your red
    blood cells and A antibodies in your blood
    plasma.
  • Blood group AB If you belong to the blood group
    AB, you have both A and B antigens on the surface
    of your red blood cells and no A or B antibodies
    at all in your blood plasma.
  • Blood group 0 If you belong to the blood group 0
    (null), you have neither A or B antigens on the
    surface of your red blood cells but you have both
    A and B antibodies in your blood plasma.
  • Instructions
  • You are provided with simulated antibodies for A
    and B blood types. The physical property you
    should observe when the blood is treated with
    antibodies is the same property observed when
    real blood is typed with protein-based
    antibodies.  Use these antibodies to type the
    provided blood samples.

23
Blood Groups
24
Simulated Blood Samples
  • Blood typing kits are available online ()
  • Solutions based on solubility can also be used
  • Example
  • Blood type A calcium nitrate solution in water
  • Antibodies for A sodium carbonate in water
  • Blood type B sodium chloride in water
  • Antibodies for B silver nitrate in water
  • Type A antibodies for A precipitation (type
    A, not 0)
  • Type A antibodies for B no precipitation (not
    type B/AB, must be type A)
  • Red food coloring can be added to all solutions
    with no effect on results

25
Analysis of the Crime
  • What does each piece of evidence mean by itself?
  • How does all the evidence fit together?
  • Make a table

X implicated by evidence
26
Tips from the Supervisor
  • A good note sheet is key
  • Have a list of possible chemical reactions, notes
    on density tests, fiber analysis, types of
    fingerprints, etc.
  • Time is a factor 33 of teams finshed at
    regional, 10 finished at state
  • Students did best on the powder and fingerprint
    tests, and struggled on polymer and fiber
    analysis.
  • Practice running chromatography

27
Additional Resources
  • Visit the Forensics webpage at the Science
    Olympiad website
  • http//www.soinc.org/events/forensics/index.htm
  • This has many links to resources that are helpful
    in preparing for the event but it doesnt look
    updated for 2008 at this point.
  • It also has links to places you can order fiber
    and polymer kits.
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