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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
Q

Biological stains can appear:

A 
reddish brown (blood)
yellowish white (semen, vaginal secretions)
Yellow (urine)

Touch DNA is not visible

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26
Q

Using an ultra violet light will:

A

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

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27
Q

Identification of Biological Evidence

A

Show that substance is blood, semen, saliva, etc.

28
Q

Individualization of Biological Evidence

A

Show who the substance belongs to through comparison with K sample

29
Q

Reconstruction of Biological Evidence

A

Interpretation of stain patterns

30
Q

Presumptive tests

A

“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
Q

Confirmatory Tests

A

specific for the substance for which they are intended

Proves that the material or substance they test for is present

32
Q

Presumptive tests qualities

A

Inexpensive
Simple
Quick
Easy to ready

non specific
may have false positives

33
Q

Confirmatory Tests qualities

A 
Expensive 
More complicated 
takes time 
need training for interpretation of results
specific 
no false positives
34
Q

Presumptive tests for blood = color tests

A 
Phenolphathalein 
O-tolidine
Tetramethelbenzidine 
Leuchomalachite green
Hemastix
Luminol Bluestar
35
Q

Crystal Tests

A

Takayama
Teichmann
Characteristic crystals form with addiction of chemical

36
Q

Immunological

A

use antibody/antigen reaction for human hemoglobin

37
Q

Presumptive tests for seman

A

Acid phosphatase test

AP is an enzyme from the prostate gland found in high concentrations in human seminal fluid

38
Q

Presumptive tests for vaginal secretions

A

no reliable method for identification of vaginal fluids

39
Q

Presumptive tests for saliva

A

presence of amylase (enzyme responsible for breaking down starches)

40
Q

Presumptive tests fro urine

A

presence of urea and creatinine

41
Q

Semen

A

male reproductive fluid consisting of sperm cells suspended in seminal plasma

42
Q

Seminal plasma

A

consists of fluid contributed primarily by the prostate gland

also contains fluid from the Cowper’s gland

43
Q

Sperm

A

Spermatazoon

male reproductive cells produced in the testes and stored in the seminal vesicles until ejaculation occurs

44
Q

Semen fun fact

A

Mature, fertile males have 15 million to 80 million sperm cells per milliliter of semen

45
Q

Confirmatory test for semen

A

Christmas tree stain

Dyes heads red
dyes tails green

46
Q

Confirmatory Test for Sperm

A

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
Q

General rule for evidence collection

A

when possible, collect the entire item

48
Q

If an item of evidence is suspected to have evidence of a biological nature, it should be packaged in a:

A

paper bag or box so the evidence can “breathe”

49
Q

Blood is drawn in an

A

anticoagulant tube

50
Q

Alternative known control

A

specimen obtained from a known source that might be the source of the evidence

51
Q

blank control

A

clean sample containing no specimen that is used to ensure a test is working properly

52
Q

Collection of wet clothing

A

Paper bag

Collect last (to allow drying time)

Hang in evidence drying cabinet (or designated area)

53
Q

Evidence must be dried throughly before

A

packaging and sealing

54
Q

Evidence must be stored in a:

A

cool, dry, environment

55
Q

Darkness + warmth =

A

growth of bacteria and mold

56
Q

Direct sunlight

A

negative effects on blood DNA

57
Q

Contamination

A

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
Q

Sources of contamination

A

prior deposition of DNA in that area

First responders

Crime Scene personnel

Laboratory personnel

59
Q

Ways to minimize contamination

A

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
Q

The majority of biological evidence comes from:

A

sexual assault investigations

61
Q

Three types of sexual assault cases:

A

Unknown offender (adult/adult)

Known offender/question of consent (adult/adult)

Crimes against children

62
Q

“Child” vs “adult” =

63
Q

CT: 16 years =

A

age of consent

64
Q

CT: Under 16 years =

A

36 month difference for offender

65
Q

Evidence collected in a sexual assault investigation

A

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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