Forensic Analysis of Bullet Holes in Glass: Fracture Sequencing
This paper presents a forensic laboratory analysis of bullet holes in glass, focusing on how radial and concentric fracture patterns are used to determine the sequence in which shots were fired. When a projectile strikes glass, it produces radial fractures that spread outward from the point of impact and concentric fractures that encircle it. Because radial fractures terminate upon meeting pre-existing cracks, investigators can reconstruct the firing order. Applying this principle to five bullet holes labeled A through E, the analysis concludes that the shots were fired in the order E, B, A/D, and C, with the caveat that the relative sequence of holes A and D cannot be distinguished using this method.
- Introduction to Glass Fracture Patterns: Radial and concentric fracture types explained
- How Fracture Patterns Establish Firing Sequence: Fracture termination used to order bullet holes
- Analysis of Bullet Hole Sequence: Step-by-step sequencing of holes E, B, C, A, D
- Limitations of the Technique: Method cannot distinguish order of A and D
- References: Cited forensic investigation textbooks
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What makes this paper effective
- The paper methodically applies a clearly stated forensic principle — fracture termination indicating prior impact — to a specific, concrete case, making the reasoning easy to follow step by step.
- Each bullet hole is addressed in logical sequence, with the analysis building progressively rather than jumping between holes, which mirrors real investigative procedure.
- The author honestly acknowledges the method's limitation regarding holes A and D, demonstrating critical thinking rather than overstating the technique's power.
Key academic technique demonstrated
The paper demonstrates evidence-based deductive reasoning: a general forensic principle (radial fractures stop at pre-existing cracks) is stated, sourced, and then applied systematically to observed physical evidence to reach specific conclusions. This principle-to-application structure is a core technique in forensic science writing.
Structure breakdown
The paper opens with a theoretical grounding in glass fracture science, then transitions into a step-by-step forensic analysis of five labeled bullet holes (E → B → A/D → C). It closes by summarizing the overall firing order and identifying one key limitation — the inability to sequence holes A and D relative to each other — before listing its two references.
Introduction to Glass Fracture Patterns
Glass broken by a projectile forms two distinct fracture types: radial fractures and concentric fractures (Orthman & Hess, 2012). Radial fractures form on the side of the glass opposite the point of impact and spread outward from that point (Hess & Hess, 2012). Concentric fractures form after the radial fractures, on the same side as the impact, and encircle the point of impact (Woods, 2013).
Radial fractures terminate when they encounter fractures caused by an earlier projectile. This property means they can be used to determine the sequence of force — that is, which bullet hole was created before the others. In cases where multiple shots are fired at a glass surface such as a window, forensic investigators must establish the order in which the shots were fired (Woods, 2013). The first shot fired will produce complete, uninterrupted radial fractures, while the radial cracks from each subsequent shot will terminate upon encountering fractures produced by a previous bullet.
How Fracture Patterns Establish Firing Sequence
The principle underlying this forensic technique is straightforward: because a radial fracture cannot cross a pre-existing crack, the pattern of terminations across a pane of glass encodes the chronological order of impacts. Forensic investigators exploit this property by systematically tracing which hole's fractures are interrupted — and by which other hole's fractures — to reconstruct the firing sequence from first shot to last.
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