forensic science final

yes

do eyewitnesses have limitations?

evidence

something that tends to establish/disprove a fact

can include documents, testimony, and other objects

testimonial and physical

what are the 2 types of evidenc?

testimonial evidence

statement made under oath 

aka direct/prima Facie evidence 

physical evidence

any object/material that is relevant in a crime

aka indirect/real evidence

ex: hair, fiber, fingerprints, blood, soil, ect

1. nature of offense and the situation in which the crime is observed 

2. characteristics of witness 

3. manner in which info retrieved 

4. witness’s prior relationship with accused 

5. length between time of offense and identification

6. any prior I.D. or failure to I.D. defendant 

7. any prior I.D. of person other than defendant by eyewitness 

what are the main factors of the reliability of eyewitnesses?

1. generally more reliable than testimony

2. can prove crime committed

3. can corroborate/refute testimony

4. link suspect with victim/crime scene

5. establish I.D. of person associated with crime

6. can allow reconstruction of events of a crime

what is the value of physical evidence?

1. what is it?

2. man made/natural?

3. what is source?

4. how common is it?

5. can be I.D. from single source?

what questions do you ask about trace evidence?

gasoline made different by every company

forensics lab can I.D. brand and grade 

describe how gas can be used 

can be unique to certain areas

bathroom: talcum powder, cosmetics

kitchen: flour, spices

factory: remints of manufacturing process

describe how dust can be used 

• compare physical and chemical properties

• look at probability that each piece of evidence could be present

describe the I.D. process

class

common to group of objects/persons

individual

can be I.D. with particular person/single source 

1. color

2. physical match of broken edges

3. number of matching layers

what does they physical analysis of paint include?

compare paint evidence from scene to known source 

what is a forensic scientists job with paint?

paint

suspension of pigment in a film former

film former

usually organic polymer(s) purpose to protect surface and hold pigments

mixture of inorganic metal salts purpose is to impart color

1. art

2. decoration

3. protection on surfaces 

4. warnings

what is paint used for?

varnish

a film former, commonly polyurethane, dissolved in a solvent, which normally doesn’t contain stain, protect wood

stain

mixture of organic dyes dissolved in solvents, made penetrate wood and stain; doesn’t protect

enamee

polymer film= formed that adheres to surface and suspends pigments, paint dries by number different mechanisms 

paint chips

pieces of paint which have come off surface usually contain all layers 

paint smear

top layer pain loosened owing being wet/air oxidized, smear onto another surface after brushing contact; layer structure not present

1. color 

2. solubility

3. pyrolysis 

4. electron microscope

5. UV spectrophotometry 

what are the steps of paint analysis 

1. requires cross section

2. cant be done on smear

3. same #/order layers

4. relative thickness must be same

5. is a class test

describe color analysis of paint

acetone, dichloromethane, pyridine, acrylic lacquers are soluble in acetone

describe solubility of paint

1. analysis of film formers 

2. bulk technique, all layers analyzed together 

describe pyrolysis GC

top layer looked at

describe electron microscope portion of paint

separate pigments from film former

describe UV spectrophotometry

epidermis 

outer, surface layer of skin 

dermis

inner layer of skin

dermal papillae

between dermis and epidermis

form and pattern of the friction ridges on skin surface 

what do papillary patterns determine?

finger print

individual characteristic, comprised of a series of lines corresponding to hills and valleys; provides suction and traction

pores

openings for ducts leading from the sweat glands; each skin ridge is pop. by a single row

perspiration

discharged and deposited on surface of skin through pores

perspiration and oil from body hairy pts. transferred onto surface leaving impression of finger’s ridge patterns 

what helps lean finger print patterns?