Transcript Evidence Analyte/Characteristic Techniques Blood Ethanol

Physical Evidence
Any material either in gross or trace
quantities that can establish through
scientific examination and analysis
that a crime has been committed.
Forensic laboratories
Items of physical evidence
identification
evaluation
individualization
Physical Evidence
Any material either in gross or trace
quantities that can establish through
scientific examination and analysis
that a crime has been committed.
E x a m in a t io n a n d a n a l y s is o f p h y s ic a l
e v id e n c e
H ig h e s t d e g r e e o f s c ie n t ific c e r ta in t y p o s s ib le w ith
c u rre n t te c h n o lo g y
p h y s ic a l
id e n tific a tio n
c h e m ic a l
id e n tific a tio n
b io lo g ic a l
id e n tific a tio n
Classification of Physical Evidence
• Trace evidence
extremely small items
• Direct evidence
stands on its own to prove an
alleged fact
• Prima facie evidence
evidence established by law
• Circumstantial
evidence
incriminates a person
• Exculpatory evidence
helps to prove that an
accused individual is not
guilty
Topic I: Probability
Forensic laboratories
Items of physical evidence
identification
evaluation
individualization
Topic I: Probability
• Class characteristics
features that place the
item into a specific
category
• Individual
characteristics
features that distinguish
one item from another
of the same type
Topic II: Analytical
Techniques
Evidence
Analyte/Characteristic
Blood
Ethanol
Drugs of abuse
Composition
Color
Composition
Physical properties
Miscellaneous
Drugs of abuse
pH
Iron
Proteins
DNA
Fabric
Fibers
Shoes
Powder
Soil
Saliva stain
Clothing
Pen inks
Plastic fragments
Tire fragments
Food (poisoned)
Fingerprints
Arson samples
Techniques
Headspace analysis GC GC/MS
FT-Raman spectroscopy
Visible, diffuse reflectance spectroscopy
FT-IR microscopy
Solubility, melting point
Solid-phase extraction; LC
FT-IR
Potentiometry
UV-Visible Spectr.
Immunological tests
Short tandem repeat DNA analysis
Visible reflectance, FT-IR microscopy, FTRaman
UV–vis, Liquid Cromatography
FT-IR, UV–vis
Thermal analysis, FT-IR
Liquid- and solid-phase extraction, GC/MS
Fluorescent visualization
GC, GC/MS
Case Study
One morning in the summer of 1961, hundreds of crazed birds attacked the seaside
town of Capitola, California. The birds "cried like babies" as they dove into streetlamps,
crashed through glass windows, and attacked people on the ground. Most of the birds
were sooty shearwaters, a normally nonaggressive species that feeds on small fish and
comes ashore only to breed. The incident fascinated Alfred Hitchcock, who frequently
vacationed in nearby Santa Cruz. He included newspaper clippings about the Capitola
attack in his studio proposal for The Birds, which appeared in cinemas two years later.
In the winter of 1987, the agent that is now believed to be responsible for the Capitola
incident struck on the opposite shore of the continent. This time, it struck higher on the
food chain. Over a hundred people became extremely ill within hours after dining on
cultured blue mussels in restaurants around Prince Edward Island in Canada. It quickly
became apparent that this was no ordinary outbreak of food poisoning. Vomiting,
cramps, diarrhea, and incapacitating headaches were followed by confusion, loss of
memory, disorientation, and (in severe cases) seizures and coma. A few exhibited
emotional volatility, with uncontrolled crying or aggressiveness. Three elderly victims
died. [Perl].
A tragic symptom of poisoning was the destruction of short term memory in about one
quarter of the survivors. They could remember nothing that happened after the
poisoning. Some were unable to recognize their surroundings or relatives. They could
learn no new facts or skills. The most severely affected lost memories several years old.
For twelve of the victims, the loss of short term memory was permanent.
Figure 1. General strategy for isolation of the toxin responsible for
amnesic shellfish poisoning. Based on a diagram by M. Quilliam and J. L.
C. Wright (Analytical Chemistry, 61, 1054 (1989)).
A band very close to the band for glutamic acid was observed in the electrophoresis of the toxic XAD-2
fraction, but not in the control fraction. It stained a distinctly different color from the glutamic acid. When
the material in the band was collected and injected onto the HPLC column, it took exactly the same
amount of time to move through the column as the toxic component found by the HPLC analysis. It also
produced exactly the same amount of toxicity as the HPLC fraction had.
Mass spectrometry was used to determine the compound's molecular weight (312 g/mol) and molecular
formula (C15H22NO6). Spectroscopic analysis revealed the presence of conjugated double bonds and
features characteristic of an amino acid. By matching the spectra with those from STN International's
Registry system, the compound was unambiguously identified as domoic acid, an triprotic amino acid:
Domoic acid in acidic solution.
Glutamic acid in acidic solution.
Domoic acid is a molecular Trojan Horse. Nerve cells mistakenly
recognize domoic acid as glutamic acid- a fatal error. Domoic acid's
structure is obviously similar to glutamic acid. But its five-sided ring
makes it less flexible than glutamate, which causes it to bind very
tightly to glutamate receptors. As a result, the excitatory effect of
domoate is 30 to 100 times more powerful than that of glutamate
[Perl].
Topic III: Statistics
The arithmetic mean is the "standard"
average, often simply called the "mean"
The standard deviation (SD) quantifies variability.
If the data follow a bell-shaped Gaussian
distribution, then 68% of the values lie within one
SD of the mean (on either side) and 95% of the
values lie within two SD of the mean. The SD is
expressed in the same units as your data.
Case Study
Table Bullets and fragments received by the FBI.
Specimen Description
Total weight, grains
Total weight,mg
CE 399 (Q1) Bullet from stretcher (lead core plus jacket)
158.6
10,277
CE 567 (Q2) Bullet fragment from seat cushion
(lead core plus brass jacket)
44.6
2,890
CE 569 (Q3) Bullet fragment from front seat (jacket)
21.0
1,361
CE 843 (Q4,5) Two lead fragments from President’s head[2]
1.65; 0.15
107; 9.7
CE 842 (Q9) Three lead fragments from Connally’s arm
0.5
32
CE 840 (Q14) Three lead fragments from rear carpet
0.9, 0.7, 0.7
58, 45, 45
CE 841 (Q15) Scraping from inside surface of windshield
None listed
Table : Individual determinations of antimony in the
FBI’s Run 4
Specimen
Weight of subfragment, mg
Sb, ppm
Q1
7.16
643
4.20
636
1.79
750
1.24
749
1.16*
749
15.55
705±60*
Table : Individual determinations of antimony in the
FBI’s Run 4
Specimen
Weight of subfragment, mg
Sb, ppm
Q9
1.92
690
2.07
662
1.34
677
5.33
676±14
Topic IV: DNA fingerprinting
• BODY FLUIDS
 Conventional serology:
 presence of blood in stains
 species identification and
ABO grouping
 is not adequately
informative to positive
identify a person
 DNA analysis can associate
victim and/or suspect with each
other or with the crime scene
• BLOODSTAIN PATTERNS
 additional information
SEM: erythrocytes & lymphocytes
Topic V: Arson and Explosives
• FIRE DEBRIS &
EXPLOSIVES RESIDUE
EXAMINATIONS
 identification of accelerants
and explosive residues
Unburned accelerator liquid on a soot covered carpet
Topic VI: Toxicology
• BODY TISSUES
 organ samples collected at
autopsy, including blood,
urine and stomach contents
• DRUGS & CONTROLLED
SUBSTANCES
 plant materials, powders,
tablets, capsules
 toxicological analysis
 volatile compounds (ethanol,
methanol, isopropanol)
 heavy metals (arsenic)
 nonvolatile organic compounds
(drugs of abuse, pharmaceuticals)
 miscellaneous (strychnine,
cyanide)
 trace drug presence, identity,
and quantity
 Black tar heroine wrapped in cellophane