Body Fluid Identification

Body Fluid ID - Crimson Canvas

Forensic body fluid identification links individuals to crime scenes under BSA evidence protocols. Key fluids: blood, semen, saliva. Blood analysis is paramount for BNS investigations.

• Blood Identification:
  • Presumptive Tests (Screening): Indicate possible presence of blood.
    • Phenolphthalein (Kastle-Meyer): Pink color with alkali & H2O2. Highly sensitive but requires confirmatory testing due to potential false positives.
    • Luminol Test: Blue chemiluminescence. Extremely sensitive, detects minute/washed/old stains but may affect DNA analysis quality.
    • Leucomalachite Green (LMG): Green color. Safer alternative to obsolete carcinogenic tests.
  • Confirmatory Tests: Confirm blood presence per BNSS evidence standards.
    • Spectroscopic Examination: Characteristic absorption bands of haemoglobin derivatives. Primary modern method.
    • Immunochromatographic Assays (Hexagon OBTI): Human-specific hemoglobin detection.
    • Teichmann/Takayama Tests: Historical crystal tests, largely superseded by advanced techniques.
  • Species of Origin: Determines if blood is human under BSA identification protocols.
    • Immunochromatographic Methods: Human hemoglobin-specific detection (e.g., Hexagon OBTI).
    • DNA-based Analysis: PCR amplification of human-specific sequences.
    • Precipitin Test (Uhlenhuth): Traditional method using Anti-Human Globulin serum.

⭐ Luminol test can detect bloodstains even after washing and in dilutions up to 1:1,000,000.

Body Fluid ID - Telltale Traces

Semen Identification

• Presumptive Tests:
  • Acid Phosphatase (AP) Test: Brentamine Fast Blue B → purple. Most common.
  • Florence Test (Iodine): Choline periodide → dark brown rhombic crystals.
  • Barberio's Test (Picric Acid): Spermine picrate → yellow needle-shaped crystals.
• Confirmatory Tests:
  • Microscopy: Spermatozoa identification (Christmas Tree Stain: red heads, green tails). Gold standard.
  • Prostate-Specific Antigen (PSA/p30): Highly specific, even in aspermia.
  • Semenogelin (Sg).
• Persistence:
  • Vagina: Motile 24-72 hrs; Non-motile up to 7-10 days.
  • Dried stains: Years.

⭐ Spermatozoa can be detected in the vagina for up to 7-10 days post-coitus, though motility is lost much earlier (24-72 hours).

Saliva Identification

• Presumptive Tests:
  • Starch-Iodine Test: Amylase (ptyalin) digests starch → colorless area on blue/purple background.
  • Phadebas Test: Amylase activity → blue dye released. More specific than starch-iodine.
• Confirmatory Tests:
  • High levels of α-amylase (salivary isoenzyme).
  • Buccal epithelial cells (microscopy).
  • mRNA profiling (e.g., STATH, HTN3).

Body Fluid ID - Subtle Signs & Frontiers

• Urine
  • Traditional serological methods: Urea (DMAC test), creatinine (Jaffe's test), Tamm-Horsfall protein (THP) are considered presumptive.
  • Characteristic odor, urochrome pigment.
• Sweat (Perspiration)
  • Key Markers: Urea, lactate, amino acids.
  • Difficult to confirm definitively; often relies on circumstantial evidence and epithelial cell DNA.
• Vaginal Secretions
  • Traditional methods: Glycogenated squamous epithelial cells (Lugol's iodine: Schiller's test - cells stain brown/mahogany; PAS stain positive).
  • Lactobacilli presence. Acidic pH (3.8-4.5).
  • Florence test (choline) may be positive but not specific - presumptive nature limits definitive identification.
• Menstrual Blood
  • Key Markers: ↑ D-dimer, Fibrinogen Degradation Products (FDPs), endometrial cells, glycogen.
  • Lacks fibrin clots (due to fibrinolysin).
  • Histological identification of endometrial glands/stroma.

  ⭐ Menstrual blood typically shows significantly higher levels of D-dimer compared to peripheral blood, aiding in its differentiation.

• Modern Definitive Methods
  • DNA Methylation Analysis: Distinguishes between blood, saliva, semen, and vaginal secretions definitively.
  • mRNA Profiling: Identifies fluid type by analyzing gene expression patterns from abundant mRNA present (e.g., HBB for blood, STATH for saliva).
    • miRNA: High stability, body fluid ID, wound/injury age estimation.
  • Microbial Profiling: Distinguishes between saliva, blood, male urine, female urine, feces, semen, menstrual and vaginal secretions.
  • Advantages: More specific, less destructive, can identify mixed body fluids simultaneously.

High‑Yield Points - ⚡ Biggest Takeaways

• Semen: Acid Phosphatase (AP) and PSA (p30) for screening; modern analysis emphasizes DNA profiling (STR) from sperm cells for individual identification under BSA provisions.
• Saliva: α-Amylase (Phadebas test) with mRNA profiling for salivary-specific genes; DNA analysis for individualization per BNSS procedures.
• Blood: Kastle-Meyer and Luminol for presumptive testing; confirmatory immunochromatographic tests and DNA profiling mandatory under BNS evidence requirements.
• Urine: Urea (DMAC) and creatinine (Jaffe's) markers; DNA analysis from epithelial cells for identification.
• Vaginal Secretions: Lugol's iodine staining; mRNA markers and DNA analysis for definitive identification.
• Menstrual Blood: Microscopic examination with endometrial cells; mRNA profiling preferred over D-dimer alone.