Forensic Biology: Blood Examination and Identification

Comprehensive practice questions covering blood composition, hematology, forensic presumptive and confirmatory testing, and laboratory collection procedures.

What percentage of the human body's weight is comprised of blood?

Approximately $8\%$.

What is the average blood volume for males and females?

Male: $5-6\,L$; Female: $3-4\,L$.

How is the total blood volume divided between formed elements and blood plasma?

Formed elements comprise approximately $45\%$ and blood plasma comprises approximately $55\%$ of the total blood volume.

What are the primary characteristics of Red Blood Cells (erythrocytes)?

They are donut-like, biconcave discs, lack nuclei in circulation, have a life span of $100 - 120\,days$, and contain hemoglobin.

What is the concentration of Red Blood Cells per microliter of blood?

$\sim 4.5 \text{ to } 6 \times 10^{6}$ RBCs per $\mu L$ of blood.

What is the function of hemoglobin (Hb) and what percentage of an RBC's weight does it constitute?

It is responsible for oxygen transportation and constitutes approximately $33\%$ of the cell weight.

What are the five types of White Blood Cells (leukocytes)?

Lymphocytes, Monocytes, Neutrophils, Basophils, and Eosinophils.

What is the concentration of White Blood Cells per microliter of blood?

$\sim 5 \text{ to } 10 \times 10^{3}$ per $\mu L$ of blood.

What are thrombocytes and what is their concentration in blood?

Also known as platelets, they participate in blood clotting and have a concentration of $\sim 200 \text{ to } 400 \times 10^{3}$ per $\mu L$ of blood.

How is serum defined in forensic biology?

Serum is blood plasma with the clotting factors removed.

What is Hematopoiesis?

The production of blood cells, which in normal adults occurs in the bone marrow and lymphatic tissues.

What is the molecular weight of a hemoglobin molecule?

Approximately $64,500\,Daltons$.

What are the two components that make up a heme portion in hemoglobin?

Globin (protein) and Heme (pigment containing iron).

What is the difference between Ferric Heme and Ferrous Heme regarding blood age?

Ferric Heme (met-Hgb) is oxidized and found in dried blood, while Ferrous Heme is reduced and found in fresh blood.

Why is an IR camera useful for locating bloodstains?

It allows for the identification of bloodstains on dark fabrics without the need for chemical reagents.

What is the general chemical principle behind presumptive color tests for blood?

They are oxidation/reduction reactions where heme acts as a catalyst to break down $H_2O_2$.

Which presumptive test is specifically used for non-visible bloodstains and produces a bluish white luminescence in the dark?

Luminol.

What distinguishes Bluestar from Luminol in forensic field use?

Bluestar has stronger and longer-lasting luminescence and does not require total darkness to be visible.

What is Leucocrystal Violet (LCV) primarily used for in forensic investigations?

Enhancing blood footwear impressions.

What is the positive result indicator for the Tetramethylbenzidine (TMB) test?

An immediate blue-green color change after the addition of $H_2O_2$.

What does a blue-green color change before adding $H_2O_2$ in a TMB test indicate?

An inconclusive test result, likely due to the presence of other oxidizing agents (false positive).

What are the insoluble red feathery crystals formed during a positive Takayama test?

Pyridineferroprotoporphyrin crystals (also called hemochromogen crystals).

What is the purpose of the Ouchterlony test?

Species determination through a precipitin reaction.

What is the current test used by BCI for human identification in bloodstains?

HemDirect (a one-step chromatographic immunoassay for human hemoglobin).

According to the lecture, the HemDirect test is known to cross-react with which animals?

Upper primates and ferrets.

What are the three bloodstain collection techniques mentioned?

Scraping, Cutting, and Transferring (swabbing).

In a forensic laboratory, what is the purpose of a 'Control' sample?

To ensure typing results are from the stain itself and not from the substrate (material) on which the stain was deposited.