Unit 07 · Ballistics & Toolmarks
A fired bullet and a pried lock both carry marks — and reading them is careful, comparative work, not a certainty. This unit covers how firearms and cartridges leave their signatures, how rifling produces striations that can be compared under the comparison microscope, how toolmarks are matched and where that matching reaches its limits, and how trajectory and the physics of the scene — angles, distance, geometry — constrain what could have happened. Mastery means you can compare marks, document what you see, and report consistency and confidence rather than proof.
| Criterion | Not yet | Approaching | Mastered |
|---|---|---|---|
| Firearm & cartridge basics | Cannot say how a fired cartridge picks up marks. | Names parts but not how firing and extraction leave marks. | Explains how a firearm and cartridge produce the marks an examiner later compares. |
| Rifling & striation comparison | Cannot use the comparison microscope to align striations. | Aligns marks but reads agreement inconsistently. | Compares rifling striations on the comparison microscope and describes the degree of agreement it shows. |
| Toolmark comparison & its limits | Declares a toolmark a certain match. | Compares marks but overstates the strength of the finding. | Compares toolmarks and reports consistency and a level of confidence, explaining why an examiner does not claim certainty. |
| Trajectory & the physics of the scene | Ignores angle, distance, or geometry at the scene. | Estimates a path but cannot justify it from the geometry. | Uses angles, distance, and geometry to constrain a trajectory, stating the uncertainty in the reconstruction. |
| Technique & documentation | Handles or records evidence without a clear method. | Documents unevenly or leaves gaps in the record. | Handles evidence with consistent technique and documents each comparison so another examiner could follow it. |
| 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 striations on the two bullets line up well under the comparison microscope, so I’d report the marks as consistent, with a high degree of confidence — but I wouldn’t call it a certain, one-and-only match. What that consistency means for the case is for the court to weigh.”
“The marks look the same, so it’s definitely the same gun — that proves he fired it.”
You demonstrate this unit by comparing marks on the comparison microscope and reconstructing a trajectory, explaining aloud what the geometry supports — not a multiple-choice test. A criterion counts as mastered only when your documentation is reproducible and you report consistency and confidence rather than certainty. 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.