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Intro to Forensic Science > Biological Evidence > Flashcards

Biological Evidence Flashcards

1
Q

Biological Evidence

A 
Blood 
Seminal fluid 
Vaginal secretion 
saliva 
urine 
touch DNA (skin cells)
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2
Q

You will find biological evidence:

A

homicide
sexual assault
weapons
assault (stabbing, shooting, fight)

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3
Q

Forensic biology

A

preliminary examination of biological evidence in blood transfer and sexual assault cases

Precursor for DNA analysis

may also refer to forensic botany

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4
Q

Forensic serology

A

preliminary examination and genetic typing of biological evidence in blood transfer and sexual assault cases before DNA analysis was available

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5
Q

DNA typing developed in the

A

1980s

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6
Q

blood typing

A

possible linkage, not individualization

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7
Q

What is blood?

A

tissue
liquid
made up of water, cells, enzymes, proteins, glucose…
circulates throughout the body

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8
Q

Purpose of blood

A

supplies nutrients and oxygen in the body

carries hormones and other ingested substances throughout the body

removes waste

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9
Q

Blood cells contained within blood:

A

red and white blood cells (they are very different)

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10
Q

Serum

A

straw colored liquid portion of blood that remains after whole blood has been allowed to clot

contains dissolved proteins and antibodies

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11
Q

Plasma

A

straw colored liquid portion of blood that remains after blood cells have settled (NOT clotted)

Contains clotting proteins

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12
Q

Red blood cells

A

have no nucleus

not useful for DNA analysis

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13
Q

White blood cells

A

WBC have a nucleus

Useful for DNA analysis

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14
Q

Platelets

A

Irregularly shaped colorless bodies

Produced in the bone marrow

Sticky surface lets them help form clots to stop bleeding

active only when damage occurs to circulatory system walls

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15
Q

Amount of blood at a crime scene depends on:

A

active flow and passive flow

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16
Q

Active flow

A

the heart is still pumping

example: injury to jugular - arterial spurting

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17
Q

Passive flow

A

no blood pressure

Blood flow following death

Example: gunshot to heart - blood pool near body

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18
Q

Hemoglobin

A

Found in RBC

Peroxidase like activity

Used as a basis for reactions with presumptive reagents

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19
Q

Blood Group Antigen

A

Found in RBC

Bound to RBC membrane

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20
Q

DNA

A

Found in WBC

Found in cells with nucleus

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21
Q

Proteins

A

Found in PLASMA

Serum used in species testing

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22
Q

The first step in crime scene and evidence processing is:

A

recognition

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23
Q

Biological stains can be found:

A

literally anywhere

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24
Q

Biological stains can be:

A

wet
dry
singular evidence
on other items of evidence

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25
Biological stains can appear:
``` reddish brown (blood) yellowish white (semen, vaginal secretions) Yellow (urine) ``` Touch DNA is not visible
26
Using an ultra violet light will:
cause semen, vaginal secretions, and urine to fluoresce (using an orange filter) reemits UV light Cause blood to appear black (absorbs UV light) Preliminary examination of evidence only UV light is not a presumptive test
27
Identification of Biological Evidence
Show that substance is blood, semen, saliva, etc.
28
Individualization of Biological Evidence
Show who the substance belongs to through comparison with K sample
29
Reconstruction of Biological Evidence
Interpretation of stain patterns
30
Presumptive tests
"Screening" tests Preliminary test Used for non definitive testing of specimens that may be biological in nature Gives an indication that a substance may be present
31
Confirmatory Tests
specific for the substance for which they are intended Proves that the material or substance they test for is present
32
Presumptive tests qualities
Inexpensive Simple Quick Easy to ready non specific may have false positives
33
Confirmatory Tests qualities
``` Expensive More complicated takes time need training for interpretation of results specific no false positives ```
34
Presumptive tests for blood = color tests
``` Phenolphathalein O-tolidine Tetramethelbenzidine Leuchomalachite green Hemastix Luminol Bluestar ```
35
Crystal Tests
Takayama Teichmann Characteristic crystals form with addiction of chemical
36
Immunological
use antibody/antigen reaction for human hemoglobin
37
Presumptive tests for seman
Acid phosphatase test AP is an enzyme from the prostate gland found in high concentrations in human seminal fluid
38
Presumptive tests for vaginal secretions
no reliable method for identification of vaginal fluids
39
Presumptive tests for saliva
presence of amylase (enzyme responsible for breaking down starches)
40
Presumptive tests fro urine
presence of urea and creatinine
41
Semen
male reproductive fluid consisting of sperm cells suspended in seminal plasma
42
Seminal plasma
consists of fluid contributed primarily by the prostate gland also contains fluid from the Cowper's gland
43
Sperm
Spermatazoon male reproductive cells produced in the testes and stored in the seminal vesicles until ejaculation occurs
44
Semen fun fact
Mature, fertile males have 15 million to 80 million sperm cells per milliliter of semen
45
Confirmatory test for semen
Christmas tree stain Dyes heads red dyes tails green
46
Confirmatory Test for Sperm
If no sperm are present in the seminal fluid (biological issues, vasectomy, etc) test for the following: P30 prostate gland protein/ prostate specific antigen (PSA) Found to be almost unique to human semen
47
General rule for evidence collection
when possible, collect the entire item
48
If an item of evidence is suspected to have evidence of a biological nature, it should be packaged in a:
paper bag or box so the evidence can "breathe"
49
Blood is drawn in an
anticoagulant tube
50
Alternative known control
specimen obtained from a known source that might be the source of the evidence
51
blank control
clean sample containing no specimen that is used to ensure a test is working properly
52
Collection of wet clothing
Paper bag Collect last (to allow drying time) Hang in evidence drying cabinet (or designated area)
53
Evidence must be dried throughly before
packaging and sealing
54
Evidence must be stored in a:
cool, dry, environment
55
Darkness + warmth =
growth of bacteria and mold
56
Direct sunlight
negative effects on blood DNA
57
Contamination
Unintended, potentially unrecognized, biological material in or on a biological evidence specimen, which could cause difficulty in interpreting the results of some of the tests.
58
Sources of contamination
prior deposition of DNA in that area First responders Crime Scene personnel Laboratory personnel
59
Ways to minimize contamination
limit the number of people at the scene Personal protection equipment Change gloves before handling each new piece of evidence Change gloves after touching non evidentiary items Collect substrate control for potential lab examination Use disposable tweezers/forceps for collection of small items Use properly ventilated containers for packaging
60
The majority of biological evidence comes from:
sexual assault investigations
61
Three types of sexual assault cases:
Unknown offender (adult/adult) Known offender/question of consent (adult/adult) Crimes against children
62
"Child" vs "adult" =
age
63
CT: 16 years =
age of consent
64
CT: Under 16 years =
36 month difference for offender
65
Evidence collected in a sexual assault investigation
CT-100 Sexual Assault Evidence Collection Kit Clothing Bedding Condom and Wrappers Objects used during assault Evidence from suspect

Intro to Forensic Science (12 decks)

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