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Serology

A branch of science dealing with the measurement and characterization of antibodies, antigens, and other immunological substances in blood.

Antigen

A substance (usually a protein) that stimulates the body to produce antibodies.

Antibody

A protein in blood serum that destroys or inactivates specific antigens.

Presumptive Testing

A screening test used when a fluid is suspected to be blood or semen, based on a visible color change.

Confirmatory Testing

A test performed after a presumptive test to confirm the presence of a specific body fluid.

Kastle-Meyer Test

Presumptive test for blood that turns pink in the presence of hemoglobin.

Acid Phosphatase Test

Presumptive test for semen that turns purple when enzyme activity is detected.

Takayama Crystal Test

Confirmatory test for blood that forms crystals when blood is present.

RSID (Rapid Stain Identification)

Strip tests that identify specific body fluids from forensic evidence.

Red Blood Cells (Erythrocytes)

Carry oxygen; contain antigens; lack a nucleus.

White Blood Cells (Leukocytes)

Part of the immune system; have a nucleus.

Platelets (Thrombocytes)

Help with blood clotting.

Plasma

Fluid portion of blood (55%), mostly water with antibodies, vitamins, and proteins.

Rh Factor

A protein that determines whether a blood type is positive (+) or negative (-).

False Positive

A test result that incorrectly indicates the presence of a substance.

False Negative

A test result that incorrectly shows no presence of a substance when it is there.

Luminol Test

A sensitive presumptive test for detecting trace amounts of blood via chemiluminescence.

Seminal Fluid

Fluid containing sperm and other components like sugars, proteins, and ions.

Oligospermia

Medical condition causing low sperm count.

Aspermia

Medical condition resulting in no sperm production.

Vasectomy

A surgical procedure preventing sperm production.

p30 (Prostate-Specific Antigen)

Glycoprotein used to confirm semen presence; produced by prostate gland.

Christmas Tree Staining

A technique using red and green stains to identify sperm cells microscopically.

Amylase

An enzyme found in saliva and pancreas that digests starch.

Phadebas Amylase Saliva Test

Saliva test using a tablet that turns blue when amylase breaks down starch.

DNA (Deoxyribonucleic Acid)

A chain of chemical building blocks (G, A, T, C) that carries genetic information.

Short Tandem Repeats (STRs)

Non-coding DNA sequences made of repeating units; used in DNA profiling.

Epithelial Cells

Skin cells that can leave DNA traces even without visible stains.

Contamination

The unintentional addition of external material or DNA to a crime scene or evidence.

Direct Transfer

DNA or cells transferred directly by touching.

Indirect Transfer

DNA transferred without direct contact (e.g., via another object or person).

Aerosol Transfer

DNA transferred through saliva by sneezing, coughing, or talking.

Secondary Transfer

DNA transferred through another person or object.

Tertiary Transfer

DNA transferred through multiple indirect steps.

Extraction

The process of isolating DNA from evidence.

Quantitation

Measuring the amount of DNA in a sample.

Amplification (PCR)

Polymerase Chain Reaction; technique used to copy DNA segments.

Capillary Electrophoresis

Technique to separate DNA fragments by size for analysis.

DNA Profile

A string of numbers representing STR results used to identify or compare DNA samples.

GeneMapper / GeneMarker

Software used to analyze and visualize DNA data.

CODIS (Combined DNA Index System)

National DNA database used for comparing DNA profiles.

Inclusion

DNA match with known sample.

Exclusion

DNA does not match known sample.

Amelogenin

A genetic marker used to determine biological sex (X or Y chromosome).

Alternate Light Source (ALS)

Tool used to detect stains and fluids invisible to the naked eye.

Chelex®

Chemical used in DNA extraction from blood, saliva, semen, and hair.

Real-time PCR (Quantifiler Trio)

A method to quantify tiny amounts of DNA—sensitive to ~37.5 pg.

STR Typing Result

The output of STR analysis represented by repeat numbers at specific loci.

Forensic DNA Limitations

Cannot determine race, age, time of deposition, or personal traits.

Locard’s Exchange Principle

“Every contact leaves a trace” – used in forensic evidence analysis.