Serology

Question 1

Why is it used?

Answer 1

Used more as a screening method to see if there is a need to take a sampling of evidence for DNA

Question 2

What is the definition of serology?

Answer 2

Defined as the examination and analysis of body fluids

Question 3

what are the types of body fluid testing?

Answer 3

Blood, saliva, semen, and urine

Question 4

Presumptive testing

Answer 4

Analyze a sample and establish one of the following:
1. The sample is definitely not a certain substance
2. The sample probably is the substance

A positive reaction indicates the possibility of X
- Important to remember indicates not specific for
- Ex. bleach would test positive
- It tests for what you’re looking for, but also could be positive for other things as well. It’s probably blood, but because it can react with other things, we cannot say it is definite

“Presumptively positive for whatever you are testing for. It is indicating it, but does not mean specifically that it is there.”
- It could show positive for blood, but could be bovine or canine

Question 5

Confirmatory testing

Answer 5

• Required to confirm the analysis
• Confirmatory tests cost more than simpler presumptive tests so presumptive tests are often done to see if confirmatory tests are necessary
• Usually takes more time as well

Question 6

4 S’s of Choosing a Reagent

Answer 6

Sensitivity
Specificity
Safety
Simplicity

Question 7

Sensitivity

Answer 7

Neat: body fluid in its natural state (not diluted in any way)
Ex. Vaginal fluid and saliva with dilute semen

Question 8

specificity

Answer 8

You want a test that tests for what you are testing for. You don’t want one that tests for 30 things, but rather 3.

Question 9

safety

Answer 9

Can be performed on a crime scene or at a lab

Question 10

simplicity

Answer 10

At a crime scene you want to go with less is more

Question 11

Target stain must be _____ for genetic testing

Answer 11

viable

Question 12

What are other important considerations for choosing a reagent

Answer 12

Substrate and environmental conditions may be important considerations (what works well in the lab may be cumbersome in the field)

Question 13

Benzidines and Derivatives

Answer 13

Used extensively as blood detection reagents because of their good sensitivity

Active dye in Hemastix

Question 14

What is the active dye in hemastix?

Answer 14

Benzidines and Derivatives

Question 15

How do hemastix work?

Answer 15

Constructed by embedding active materials at end of a plastic strip contributes to the safety and ease of use for testing

Hemastix is a one step test since both parts of the test are contained in the stick

Presumptive

Always required to do a positive and negative control before using at a scene

Question 16

What is a substrate control?

Answer 16

A small unstained portion of whatever you are testing to show that the substance itself is what is making it turn and not a dye coming off the carrier

(do not do it on an area not in question)

Question 17

what is the most common presumptive test used in blood identification?

Answer 17

Triarylmethanes
(similar to Phenolphthalein tests)

Question 18

What are the Triarylmethanes

Answer 18

Phenolphthalein (Kastle-Meyer Reagent), Leucomalachit Green, Leucrystal Violet and Fluorescein

Structural variations give rise to their different color reactions and cause the reaction to fluoresce (fluorescein)

PhenolphthaLIN (colorless and reduced form of phenolphthalein) + H2O2

Reacts with hemoglobin

Always use a (+) control

read results immediately

very high sensitivity

false positives

Question 19

Phenolphthalein AKA (Kastle-Meyer reagent)

Answer 19

Take phenoLIN to hydrogen peroxide and it turns pink, it’s a positive

But if it turns pink before adding the hydrogen peroxide, it is a compromised test and not valid.

Always need to do a control (around once a day is usually good)

Wait to make sure there is no reaction

Question 20

Steps to conduct a Kastle-Meyer test

Answer 20

1. Moisten swab with distilled H2O
2. Swab area you want to test
3. Add drop of ethanol (no color change) - Increases sensitivity of the test
4. Add a drop of phenolphthalein (should be no color)
5. Add a drop of h2o2

Question 21

Chemiluminescence (and types)

Answer 21

process by which light is emitted as a product of a chemical reaction; no additional light is required for the reaction to take place (Luminol)

First made in 1853

First used in the application FS in 1937

In 1951, Grodsky combined luminol, sodium perborate, sodium carbonate, and distilled water which is the common mixture used today

Good because it can be used on really old stains

Bluestar is also a type

Question 22

Fluorescence (and types)

Answer 22

occurs when a chemical substance is exposed to a particular wavelength of light and light energy is emitted at longer wavelengths

Fluorescein
- catalytic reaction between the hemoglobin, blood, and oxygen
- very good on latent bloodstaines
- longer half-life
- does not react with bleach

Question 23

Luminol test

Answer 23

Luminol + Oxidizer → chemiluminescence

Reacts to the hemoglobin in the RBC

More luminol must be added for further chemilumi to occur

Light blue glow
- Bleach tends to appear white

As you add more luminol, you are diluting the stain though so you have to be careful

Question 24

Bluestar test

Answer 24

Competeter of luminol

Fairly new forensic tool (2000)

Derivative of luminol

Application by atomizing/ light spraying

Stringer and longer lasting luminescence than luminol

Do not need complete darkness

Lasts for a couple days once mixed

Question 25

Crystal/ microcrystal test

Answer 25

Confirmatory testing

Teichmann Test:
- Heating dried blood in the presence of glacial acetic acid and a halide (usually chloride) to form the hematin derivative
- Crystals are observed microscopically
- Rhombic in shape; brownish in color

Takayama:
- Biggest issue for both is that you cannot go backwards
- Get the rest from slides

Question 26

Immunoassay confirmation of blood

Answer 26

Hexagon OBTI and Hematrace

Human specific test for blood

+ result indicates a strong likelihood for the presence of human blood

Must still confirm in lab

Sometimes positive for animals (primates)

Question 27

Seratec PMB test

Answer 27

chromotpgraphic immunoassay

rapid detection human blood and/ or menstrual blood

sexual assault cases- blood evidence is found on victim’s undergarments

want to rest the common claim made by alleged aggressors that the evidence is menstrual blood, resulting naturally, instead of peripheral blood, resulting from sexual assault.

want to conform blood is human and exclude the possibiliy it is menstrual

Question 28

Ouchterlony double diffusion

Answer 28

Carried out in AGAR Gel

Holes are punched

Antiserum is placed in center well

Different stain extracts around

Incubate about 24 hours

Question 29

Acid Phosphatase is for identifying what?

Answer 29

Semen

completely presumptive

Question 30

What is PSA or P30

Answer 30

Prostate is the source of the enzyme AP and the protein prostate specific antigen (PSA)

Negative AP does not mean that semen is not present, just that it may not be present in a detectable level

Read in 10 minutes

Can also have the hook issue, so have to dilute

P30 card is helpful because vasectomized men don’t have semen

Question 31

What is a christmas tree stain?

Answer 31

Nuclear fast red + picroindicocarmine

sperm heads (acrosomal cap) remain white

posterior portion of sperm is pink/ purple

epithelial cells are green with pink/ red nuclei

Question 32

What is the main enzyme in saliva?

Answer 32

beta amylase

Question 33

How does saliva identification work?

Answer 33

Comprised of water, mucus, proteins, salts, and enzymes in the mouth

Humans produce 1 to 1.5 liters of saliva per day

Primary purpose: aid in the initial stages of digestion by lubricating food masses for easier swallowing and initiating the digestion of starches using the enzyme amylase

Forensic tests detect alpha-amylase

Amylases break down starch, amylose and amylopectin smaller less complex sugars
Other fluids can have alpha-amylase, but none as much as saliva

Reagent used: Phadebas