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Forensic Final > Serology > Flashcards

Serology Flashcards

1
Q

What is serology?

A

defined as the medical science of dealing with serums

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2
Q

What is serum?

A

Serum is the clear yellowish fluid obtained when whole blood is separated into its solid and liquid components

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3
Q

What is forensic serology?

A
  • blood is analyzed to determine its source (at a crime scene or on an object)
  • deals with: blood, semen, saliva, urine, feces
  • often degraded or in stain form
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4
Q

What are the effects of sample degradation? (ie: what do the quality and condition of a sample stain affect?)

A
  • the type of analysis that can be preformed
  • whether analysis can be preformed at all
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5
Q

Evidence condition is key to its introduction to court, what can it be compromised by?

A
  1. break in the chain of custody
  2. degradation of sample due to inadequate storage
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6
Q

When examining dried blood what questions should you be prepared to anwser?

A
  1. is it blood?
  2. from what species did the blood originate?
  3. if the blood is of human origin, how closely can it be associated to a particular individual?
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7
Q

What is the proper scientific approach of examining blood? (5 steps)

A
  1. careful visual examination of the item or evidence to locate any stains or material visibly characteristic of blood
  2. application of suitable presumptive screening test
  3. application of a specific and sensitive test to confirm blood presence
  4. determination of biological species (animal or human) origin
  5. characterization of the blood using one or more genetic markers
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8
Q

What is blood made up of?

A
  1. cellular portion - 45%
    - red blood cells
    - white blood cells
    - platelets
  2. fluid portion - 55%
    - plasma
    - formed principally of water
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9
Q

What are platelets?

A
  • smallest of the formed elements
  • involved in clotting
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10
Q

What are erythrocytes?

A
  • transport oxygen and carbon dioxide throughout the body via the circulatory system
  • accomplished by hemoglobin
  • do not contain nuclei
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11
Q

What are leukocytes?

A
  • active in the immune system
  • neutrophils - the most common white blood cell, is important in the removal of bacteria and parasites from the body
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12
Q

How do you identify is a body fluid is blood, semen or saliva?

A
  • visual examination
  • presumptive testing is
    highly sensitive but not specific for a particular substance
  • confirmatory testing yields positive results for the substance in question and only that substance
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13
Q

What is visual examination for blood?

A
  • looking for reddish brown staining on items
  • can use an alternate light source to locate blood on dark items (blood will absorb the light and appear darker than surrounding material)
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14
Q

What do presumptive tests for blood do?

A

tests for blood to react with the hemoglobin present in the blood

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15
Q

Whats the most common presumptive test?

A

catalytic colour

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16
Q

What substances can interfere with a presumptive blood test?

A
  • enzymes
  • oxidizing chemicals and metals - like copper and iron
17
Q

How are presumptive tests done if area is large?

A

chemicals like luminol or fluorescein are sprayed onto the surface and visualized with an alternate light source

18
Q

What is the oldest chemical confirmatory test for blood?

A
  • using the formation of specific crystals
19
Q

What is the Takayama confirmatory test?

A
  • ferrous iron from the hemoglobin reacts to produce red feathery crystals
20
Q

What is the Teichmann test?

A
  • mixture of chemicals heated to react to hemoglobin
  • converts hemoglobin to hemin which creates brownish-yellow rhomboid crystals
21
Q

What are antigens?

A
  • any substance which provokes an adaptive immune response
  • located on the surface of red blood cells and are responsible for blood type characteristics
22
Q

What is the ABO blood grouping system?

A
  • A, B, O, refer to antigens on the surface of the red blood cells
  • corresponding antibodies - anti-A and anti-B exist in plasma
23
Q

What happens if blood of different types are mixed?

A
  • blood will agglutinate or clump together
24
Q

Is blood typing still conducted in forensic labs?

A

no

25
Q

How do you determine a species with blood?

A
  • serum protein analysis
26
Q

Why do forensic labs often test for semen?

A

crimes that involve sexual offences and require testing for the presence of semen

27
Q

How do you visually examine for semen?

A
  • white yellowish staining
  • can use alternate light source and goggles to visualize
28
Q

What is the most definitive test for visually identifying semen?

A

microscopic identification

29
Q

What is the most common presumptive test for semen?

A
  • acid phosphate test
  • positive indicated by purple
30
Q

What is a microscopic confirmatory test for semen?

A
  • Christmas tree stain
  • stains head read and tail green
31
Q

What is a chemical confirmatory test for semen?

A
  • test for p30, a prostate specific antigen
  • similar to blood test
32
Q

What evidence is collected from medical examination of a sexual assault victim?

A
  • Pubic Combings
    ◦ Pubic Hair Controls (15-20)
    ◦ External Genital Swabs
    ◦ Vaginal Swabs
    ◦ Cervix Swabs
    ◦ Rectal Swab
    ◦ Swabs of body areas
  • Oral Swabs
  • Head hairs (25)
  • Blood Sample
  • Buccal Swab
  • Fingernail Scrapings
  • Urine Specimen
  • All Clothing
33
Q

How long do seminal constituents persist in the vagina?

A
  • motile sperm: 4-6 hours
  • non-motile sperm: 3-6 days
  • seminal acid phosphatase: less than 48 hours
  • prostate specific antigen: less than 72 hours
34
Q

What evidence situations can saliva be used in?

A
  • bite marks, licked adhesive, eating and drinking surfaces, expectoration
  • detection may be difficult
35
Q

How can you visualize saliva?

A
  • can be visualized with an alternate light source
  • saliva will fluoresce
36
Q

How do you pack biological evidence?

A
  • before the collection of biological evidence begins, it is important that it be photographed and recorded on sketches
  • wearing disposable latex gloves while handling evidence is required
  • the packing of biological evidence in airtight or plastic containers must be avoided because the accumulation of residual moisture could contribute to the growth of DNA-destroying bacteria or fungi
  • each stained article should be packaged separately in a paper bag or well ventilated box
  • all biological evidence should be refrigerated or stored in a cool location until delivery to the lab

Forensic Final (13 decks)

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