Forensic Science Quiz: Blood Identification

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Questions and Answers

What principle is associated with Edmond Locard?

Every contact leaves a trace (correct)

Distinguishing animal and human proteins

Confirmatory test for hemoglobin

Blood grouping system

Which discovery is Karl Landsteiner known for?

The ABO blood grouping system (correct)

Methods for grouping dried blood stains

Rhesus blood factors

Bi-directional transfer of material

Who developed the first confirmatory test for hemoglobin?

Ludwig Teichman (correct)

Edmond Locard

Paul Theodor

Leones Lattes

What did Leones Lattes contribute to forensic analysis?

Classifying blood groups from dried stains Signup and view all the answers

Which of the following events took place in 1915 concerning blood identification?

Establishment of the Rhesus blood factors Signup and view all the answers

Who developed the original species identification test in 1949?

Ochterlony Signup and view all the answers

What significant technique did Kary Banks Mullis invent in 1986?

Polymerase chain reaction Signup and view all the answers

Which case in 1963 was significant for involving the suppression of evidence that could have favored the defense?

Brady v Maryland Signup and view all the answers

What was the primary focus of Eduard Piotrowski's research in 1985?

Blood spatter patterns Signup and view all the answers

What average terminal velocity was noted for a falling blood drop according to Herbert Leon MacDonell?

25.1 feet/second Signup and view all the answers

Which year did Alexander Jefferies publish his seminal work in DNA fingerprinting?

1984 Signup and view all the answers

In what decade was the first official studies on blood stain patterns conducted?

1970s Signup and view all the answers

Who conducted significant work on blood spattered patterns in 1939?

Victor Balthazard Signup and view all the answers

What color indicates a positive result when using Hemastix?

Green Signup and view all the answers

Which of the following statements about luminol is true?

It allows for fluorescence as an indicator. Signup and view all the answers

What is the main disadvantage of using Hemastix at a crime scene?

It can disrupt DNA profiling. Signup and view all the answers

What is the primary function of spectroscopy in lab analysis?

To distinguish between hemoglobin and its derivatives Signup and view all the answers

Which reagent is NOT used in the preparation of leucomalachite green tests?

Sodium chloride Signup and view all the answers

What is a requirement for microscopy analysis of dried stains?

Cells must be fixed and stained. Signup and view all the answers

What common issue can disrupt microchemical tests for blood?

Presence of dirt and particulate matter Signup and view all the answers

Which test detects the presence of human hemoglobin and can yield false positives with ferret blood?

Hemastix test Signup and view all the answers

Which indicator is used for leucomalachite green tests?

Green Signup and view all the answers

What is the initial step in the process of homeostasis following a vascular injury?

Vasoconstriction Signup and view all the answers

What change in color typically indicates a bruise is fresh?

Black/blue Signup and view all the answers

What role do platelets play in the clot formation process?

They initiate a clotting cascade at the wound site Signup and view all the answers

Which of the following components is essential for normal clotting rates?

Calcium and vitamin K Signup and view all the answers

In blood spatter analysis, what primarily defines the shape of a blood drop in the air?

Cohesive forces within the drop Signup and view all the answers

How does blood spatter contribute to forensic analysis?

It reveals the sequence of events and droplet directionality. Signup and view all the answers

What is a characteristic of a bruise that is considered older?

Green/yellow in color Signup and view all the answers

What is the average time for clot formation in healthy individuals?

3-15 minutes Signup and view all the answers

What effect does the type of surface have on the collection of touch DNA samples?

Rough surfaces may cause swabs to shred. Signup and view all the answers

How does the presence of sweat influence the amount of DNA transferred from touching an object?

Sweat acts as a vehicle to enhance DNA transfer. Signup and view all the answers

Which scenario is likely to produce the highest amount of touch DNA?

An item that is repeatedly touched by the same person. Signup and view all the answers

What is a crucial factor to consider when swabbing surfaces for touch DNA?

Swabbing areas should be done separately if blood is present. Signup and view all the answers

In the process of electrophoresis, which statement is true regarding molecule movement?

All molecules move toward the anode. Signup and view all the answers

Which dye is commonly used to stain proteins during electrophoresis for visualization?

Ponceau red Signup and view all the answers

What is the primary purpose of conducting ABO testing in a laboratory?

To identify specific animal species in mass disasters. Signup and view all the answers

In species typing, what does cross-reactivity refer to?

Antibodies reacting with closely related species. Signup and view all the answers

What is the outcome of the Ouchterlony Double Diffusion test?

It identifies relationships between antigens and antibodies. Signup and view all the answers

What should be considered when analyzing the effects of other DNA sources on touch DNA testing?

Swabs should not touch each other during testing. Signup and view all the answers

Which factor does NOT affect the transfer of touch DNA when handling items?

The color of the object. Signup and view all the answers

Why is communication with a latent print examiner critical during DNA sample collection?

It helps decide between collecting DNA or latent prints. Signup and view all the answers

Which aspect is important for the electrophoresis technique in terms of biological markers?

It depends on the net charge of each molecule. Signup and view all the answers

What should be done if a wet swab collects a sample from a surface?

Always use an additional dry swab after. Signup and view all the answers

Study Notes

History

Edmond Locard (1877-1966): Proposed the exchange principle, "every contact leaves a trace."
Karl Landsteiner (1901): Discovered ABO blood groups.
Ludwig Teichman (1853) Developed the first confirmatory test for hemoglobin.
Paul Theodor (1901): Published the first method for distinguishing between human and animal protein.
Leones Lattes (1915): Developed methods for grouping dried blood stains.
Landsteiner and Weiner (1915): Identified Rhesus blood factors.
A. Ochterlony (1949): Developed the Ouchterlony species identification test.
Stuart Kind (1960): Introduced tests for species identification using mixed agglutination techniques.
Brian Culliford (1964): Identified polymorphic variants of the phosphoglumutase (PGM) enzyme.
Alex Jefferies (1984): Published seminal work on DNA fingerprinting, developing restriction fragment length polymorphism (RFLP).
Kary Banks Mullis (1986): Invented the polymerase chain reaction (PCR).
Herbert Leon MacDonell (1971): Outlined rules of blood spatter evidence, including the terminal velocity of a falling blood drop.
Eduard Piotrowski (1985): Published the first official studies on blood stain patterns.
Alexandre Lacassagne: Contributed to the study of gunshot wounds.
Victor Balthazard (1939): Studied blood spatter patterns.

Important Time Frames

1800s: Early attempts to identify blood stains using microscopy and tests for hemoglobin.
1923: DC court rejected the scientific validity of the polygraph test.
1955: State of Ohio v. Samuel Sheppard case: Blood spatter evidence suggested a third party was present at the crime scene, but Sheppard's DNA was excluded from testing.
1963: Brady v. Maryland case: The prosecution's withholding of a co-defendant's confession was ruled suppression of evidence favorable to the defense.
1970s: Research identified polymorphic variants for several serum proteins and blood enzymes.
1972: Giglio v. US case: Evidence from a co-conspirator was deemed unreliable due to his plea deal.

Presumptive Blood Tests

Leucomalachite Green:
- Indicator color: GREEN
- Low Sensitivity
- Most common presumptive test
- Reagent: Sodium perborate, leuco malachite green, glacial acetic acid and water
- Procedure: Add few drops of reagent to filter paper swipe of stain, then add H2O2. A rapid color change indicates blood.
Luminol:
- Indicator: FLUORESCENCE
- Very high sensitivity
- Reagent: 5-amino-2,3-dihydro-1,4-phthalazinedione
Hemastix:
- Used by responding officers at crime scenes or hospitals.
- Reagent stick is touched to suspected stain and water is added. A green color indicates blood.
- Can give false positives for gun powder residues.
- May be discouraged due to potential for interfering with DNA analysis.

Confirmatory Tests for Blood

Confirms the presence of blood.
Microchemical Tests:
- Confirm the identity of a positive presumptive test for blood.
- Takayama or Hemochromogen Test: Red feathery crystals of pyridine ferroprotoporphyrin form when ferrous iron from hemoglobin reacts with pyridine and are observed under a microscope.
- Teichman Reaction: Similar to the Takayama test, but the Takayama test is preferred due to easier crystal formation.
Microscopy:
- Used to verify the presence of blood cells in a suspected blood sample.
- Dried stains require reconstitution, re-drying, fixing, and staining for microscopy.
- The effectiveness of this method depends on the analyst's expertise and the condition of the stain.
Spectroscopy:
- Distinguishes between hemoglobin and hemoglobin derivatives.
- Reliable for older stains that tested negative with other methods.
- All hemoglobin derivatives exhibit a strong absorbance at 400-425 nm (Soret band).
Hematrace ABAcard Tests:
- Detects the presence of human hemoglobin.
- Based on antibody-antigen reactions between the sample and antibodies in the test card.
- Positive results have been reported for ferret blood.

Touch DNA

Factors impacting probative results from touch DNA:
- Shedders vs. Non-shedders: Some individuals shed more skin cells than others. Sweating can increase DNA transfer.
- Surfaces touched: Rough textures increase friction and DNA transfer. Larger surface areas result in more DNA transfer.
- Length of time touched: Repeated contact increases DNA transfer.
- Number of people touching the item: Items touched by multiple people may have complex DNA mixtures.
- Presence of other DNA sources: Items with blood or other body fluids may have overwhelming amounts of DNA.

Factors Affecting Touch DNA Sample Collection

Surface type: Rough or textured surfaces may require multiple swabs.
Size of the surface: May require more than one swab.
Cleanliness of the surface: Wet swab followed by dry swab may be necessary.
Latent print request: Latent print processing can dilute DNA samples.
Presence of other DNA: Items with blood or other body fluids should not be tested for touch DNA unless the fluid is swabbed separately.

Laboratory Analysis of Biological Samples

Electrophoresis:
- Separates molecules based on electrical charge and size.
- Positively charged molecules move to the cathode, negatively charged molecules move to the anode.
- Used in forensic science to identify biological markers for personal identification and in DNA analysis.
- Can be used to detect variations in protein charge from amino acid substitutions.
- Visualization:
  - Hemoglobin is naturally colored.
  - Other proteins, antibodies, and enzymes require staining with Ponceau red, Amido black, or Coomassie blue.
Species Typing:
- Used to identify blood proteins specific to each animal species.
- Relies on antibody-antigen interactions.
- Ouchterlony Double Diffusion:
  - Popular species determination test using immunodiffusion and precipitation.
  - Antigen and antibody are added to separate wells in an agarose gel.
  - Forming precipitin lines where antigen-antibody reactions occur.
- DNA Testing:
  - Identifies human DNA using oligonucleotide probes that hybridize to human DNA immobilized on a nylon membrane.

Blood Stain Patterns

Blood motion:
- Cohesive forces create surface tension in blood drops, resisting penetration.
- Blood drops in air are spheroidal.
Directionality:
- Blood spatter patterns provide information about the sequence of events, droplet directionality, and movement.
- A blood drop's trajectory is influenced by its contact angle with the surface and the force it hits with.
Clot formation and bruising:
- Homeostasis: The body's process of stopping bleeding. Consists of vasoconstriction, platelet activation, and coagulation.
- Platelets: Irregularly shaped, colorless cells that form clots to stop bleeding. Release fibrinogen which forms a mesh-like web to trap blood cells.
- Bruising: Caused by bleeding under the skin when superficial blood vessels are damaged. The color changes with age, progressing from black/blue to green/yellow.

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Description

Test your knowledge of key figures and principles in forensic science, particularly related to blood identification. This quiz covers contributions from Edmond Locard, Karl Landsteiner, and Leones Lattes, as well as significant historical events in 1915. Challenge yourself and see how much you know about forensic analysis!