Unit 05 · Blood & Bodily Fluids
Biological traces at a scene can point toward what happened — but only if they are read with discipline. This unit covers presumptive tests such as Kastle–Meyer and luminol that flag possible blood, the confirmatory work that establishes what a stain actually is, ABO typing that narrows a population rather than naming a person, and bloodstain pattern analysis that reconstructs geometry from a stain’s shape and angle. Mastery means you treat a positive as a lead to confirm, never a conclusion, and you keep the analyst’s job — reporting the evidence — separate from the court’s job of deciding guilt.
| Criterion | Not yet | Approaching | Mastered |
|---|---|---|---|
| Presumptive testing (Kastle–Meyer, luminol) | Treats a presumptive positive as proof that a stain is blood. | Runs the test but cannot say what a positive does and does not establish. | Uses a presumptive positive as a lead only, explaining that it flags possible blood and must be confirmed — never that it identifies blood or a person. |
| Confirmatory testing & body-fluid identification | Cannot distinguish a presumptive screen from a confirmatory result. | Names confirmatory methods but treats the acid-phosphatase screen for semen as if it were conclusive. | Sequences presumptive screening then confirmatory identification, and reports the acid-phosphatase test as a presumptive indicator for semen that still requires confirmation. |
| ABO blood typing | Claims a blood type identifies the person it came from. | Types a sample but overstates what the result proves. | Reads ABO type correctly and reports it as narrowing a population, never as identifying an individual. |
| Bloodstain pattern analysis | Reads nothing from stain shape or ignores its geometry. | Notices pattern differences but cannot estimate angle of impact or area of origin. | Uses stain shape and angle of impact to estimate the area of origin, stating the limits of the reconstruction. |
| Technique & biohazard safety | Handles simulated samples without contamination control. | Follows some precautions but cross-contaminates or documents carelessly. | Works simulated samples with disciplined contamination control and documentation, treating every sample as if integrity and safety matter. |
| Integration (cross-domain) | Treats the science as isolated facts; makes no cross-domain connection. | Names a link to history, reading, or writing but cannot defend why it matters. | Connects the unit to its anchor across History · Reading · Writing (plus chosen electives) and defends why the connection matters. |
“The Kastle–Meyer test came up positive, so this could be blood — but that’s a presumptive result, a lead to confirm, not a finding. If confirmatory work holds and the ABO type matches, I’d report that it narrows the population, not that it names a person. Whose it is, and what it means, is for the court.”
“It turned pink, so it’s definitely his blood. The type proves it was him.”
You demonstrate this unit by working simulated stains through presumptive screening and bloodstain pattern analysis, then explaining aloud what each result does and does not establish — not a multiple-choice test. A criterion counts as mastered only when your technique controls contamination and you report a presumptive positive as a lead, never a conclusion. Mastery is demonstrated, not awarded.
A 5-page clipboard packet — unit overview, key terms, the mastery rubric, anchor examples, and a score sheet you can print and grade against.