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newSchoolWorks.com › VoTechWorks › Agriculture, Environment & Public Service › Crime Scene / Forensic Technician › Bloodstain & Trace Evidence Basics › Lesson 11
AGR-CSI53-05 · Lesson 11 · 15 clock hours · field

Scene Integration: Bloodstain and Trace Evidence in a Mock Scene

Objective. Students will process a complete mock indoor crime scene containing bloodstain patterns and multiple trace evidence types, producing a full documentation and collection package

⚠ Pending professional review

This lesson, its worked examples and its practice questions has not yet been verified by a licensed professional in the field or by a certification or approval body. It is a study draft and may contain errors. Do not use it as instructions for work on a job site or on live equipment. Always follow your instructor, your supervising professional, and current official references and regulations.

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Scene Integration: Bloodstain and Trace Evidence in a Mock Scene

Processing a real crime scene requires you to combine every skill you have practiced in isolation—photography, sketching, bloodstain pattern recognition, trace evidence collection, and chain-of-custody documentation—into one coordinated package. A single missed step can compromise evidence and undermine prosecution. This lesson walks you through that complete process on a mock indoor scene.

Safety First

Before you touch anything, gear up completely. Full PPE for a bloodstain scene means nitrile gloves (double-gloving is recommended), Tyvek or equivalent disposable coveralls, eye protection, and a fitted N95 or higher respirator. Biological fluids—even simulated ones in training—establish the habit. Change gloves between handling different evidence items to avoid cross-contamination. Do not eat, drink, or touch your face while inside the scene perimeter. Bag and dispose of all consumable PPE in a designated biohazard container after the exercise.

The Initial Walk-Through

The walk-through is an assessment, not a collection. You enter the scene along a path that avoids the highest-density evidence areas, keeping your hands visible and at your sides. Your goals are to identify the boundaries of the scene, note the general layout, spot fragile or transient evidence that must be prioritized, and plan your photography and sketch strategy.

During the walk-through, mentally catalog what you see: bloodstain pattern types (drip, transfer, spatter, cast-off, wipe, swipe, and others), hair and fiber deposits, glass fragments, soil transfer, and any paint smears. Do not interpret yet—simply observe and note location.

Systematic Photography

Photograph before you move or collect anything. Use a three-level approach:

1. Overall views — overlapping photos that cover the entire scene; each shot should overlap the previous by at least one-third so no area is missed.

2. Mid-range views — each item of evidence photographed in context, showing its relationship to fixed landmarks such as a door or wall.

3. Close-up views — each item fills the frame, first without a scale, then with an ABFO No. 2 scale or ruler placed parallel to the item.

Photograph bloodstain patterns before collecting swabs or tape lifts. For patterns on vertical surfaces, photograph straight-on (perpendicular) to avoid angular distortion.

The Field Sketch

Your sketch is a permanent two-dimensional record that complements photography. It must include a north arrow, a written scale or scale bar, the date, your name, case number, and a legend identifying every symbol used. Measure the room dimensions and the location of each evidence item from two fixed, permanent reference points (triangulation or baseline method). Record measurements to the nearest tenth of an inch or nearest centimeter—be consistent.

Evidence Prioritization and the Recovery Plan

Write your recovery plan before you collect a single item. Prioritize in this order:

1. Transient evidence — anything that can be lost quickly (tracked footwear impressions near doors, loose fibers in air flow).

2. Fragile physical evidence — glass fragments that could be disturbed, hair on smooth surfaces.

3. Bloodstain swabs and tape lifts — collected after full documentation of each pattern.

4. Stable trace evidence — soil samples, paint smears.

List each item, its planned collection method, and your reasoning. This plan becomes part of your documentation package and demonstrates scientific decision-making.

Collection, Packaging, and Labeling

Assign a unique item number to each piece of evidence before collection. Write that number on the evidence tag, the packaging, and the chain-of-custody log—all three must match.

Chain of Custody

Every item number must have a complete, unbroken chain-of-custody entry from the moment it is collected until it reaches the laboratory. Each entry records who collected it, the date and time, where it was collected, and every subsequent transfer. A gap in the chain gives the defense grounds to challenge admissibility. Complete each log entry at the moment of collection—never reconstruct from memory later.

Writing the Pattern Narrative

After collection, write a narrative for each bloodstain pattern you documented. Structure each entry as follows:

1. Category identified — state the pattern type using accepted terminology (e.g., impact spatter, drip pattern, transfer pattern).

2. Documentation action taken — describe the photography angles, measurements, and any swabs collected.

3. Preliminary interpretive statement — state only what the physical evidence directly supports. Do not speculate about events or actors beyond what the pattern itself demonstrates.

Example of a supportable statement: "An area of impact spatter measuring approximately 60 cm × 40 cm was documented on the north wall at a height of 85 cm. The pattern is consistent with a medium-velocity impact to a blood source located in front of the wall." Avoid stating who caused it or when unless additional evidence supports that conclusion.

Connecting to Your Credentials

The IAI CCSI examination tests crime-scene processing knowledge including documentation methods, evidence handling, and bloodstain pattern categories. The IAI Latent Print Certification is a separate credential, but the documentation discipline—systematic, complete, and free of unsupported conclusions—carries across both. State Evidence Tech Cert programs commonly require demonstrated competency in exactly this integrated scene-processing workflow.

Key terms8

Chain of custodyA chronological record documenting every person who collected, handled, transferred, or analyzed a piece of evidence, used to prove the evidence has not been altered or tampered with.
Impact spatterA bloodstain pattern produced when a blood source is struck with force, generating droplets that travel outward from the point of impact and land on surrounding surfaces.
Transfer patternA bloodstain created when a bloody surface contacts another surface, leaving a recognizable impression such as a handprint, footwear impression, or fabric pattern.
Transient evidencePhysical evidence that is easily lost, altered, or destroyed—such as loose fibers, footwear impressions, or odors—and must be collected before more stable evidence.
Druggist foldA specific paper-folding method used to package small or trace evidence items, creating a sealed inner fold that prevents loss of material and contamination.
TriangulationA field sketching measurement method in which the distance from an evidence item to each of two fixed reference points is measured, allowing the item to be precisely plotted on the sketch.
Mid-range photographA crime-scene photograph taken at an intermediate distance to show an evidence item in context with its immediate surroundings and fixed landmarks.
Recovery planA written, prioritized list prepared before collection begins that identifies each item of evidence, the planned collection method, and the scientific rationale for the chosen order.

Worked examples3

1. You are sketching a bloodstain on the floor. Using the baseline method, you measure from a fixed baseline along the south wall: the stain is 48 inches north of the baseline and 36 inches east of the southwest corner. A second stain is 72 inches north and 18 inches east. How far apart are the two stains, to the nearest tenth of an inch?
  1. Identify the coordinates of stain 1: east = 36 in, north = 48 in.
  2. Identify the coordinates of stain 2: east = 18 in, north = 72 in.
  3. Find the difference in the east direction: 36 − 18 = 18 in.
  4. Find the difference in the north direction: 72 − 48 = 24 in.
  5. Apply the Pythagorean theorem: distance = √(18² + 24²) = √(324 + 576) = √900 = 30.0 in.
Answer: The two stains are 30.0 inches apart.
2. Your photography log shows you photographed 40 frames for overall scene coverage. The scene is a rectangular room 20 ft × 15 ft. You plan overlapping rows of photos from left to right, with each frame overlapping the previous by one-third. If each frame covers 5 ft of width, how many frames are needed per row to cover 20 ft of width with one-third overlap?
  1. Each frame covers 5 ft but overlaps the previous frame by one-third of 5 ft = 1.67 ft.
  2. Net new width covered by each additional frame after the first = 5 − 1.67 = 3.33 ft.
  3. First frame covers 5 ft; remaining width = 20 − 5 = 15 ft.
  4. Additional frames needed = 15 ÷ 3.33 = 4.5, rounded up to 5 additional frames.
  5. Total frames per row = 1 + 5 = 6 frames.
Answer: 6 frames are needed per row to cover the 20-ft width with one-third overlap.
3. You assign item numbers sequentially starting at Item 001. In one room you collect: 3 hair samples, 2 fiber tape lifts, 1 glass fragment, and 1 bloodstain swab. In the adjacent hallway you collect: 2 soil samples and 1 paint smear. What is the item number of the last item collected, and how many chain-of-custody log entries must you complete?
  1. Count items in first room: 3 + 2 + 1 + 1 = 7 items (Items 001–007).
  2. Count items in hallway: 2 + 1 = 3 items (Items 008–010).
  3. Total items collected = 7 + 3 = 10 items.
  4. Last item number = Item 010.
  5. Each item requires one chain-of-custody log entry at the time of collection = 10 entries.
Answer: The last item collected is Item 010; you must complete 10 chain-of-custody log entries.

The math in this lesson1

Learners use the Pythagorean theorem on baseline coordinates to find distance between two stains.
8.G.7
In class: Scene walk-through and assessment: wearing full PPE, students conduct an initial walk-through of a pre-set mock scene (minimum four bloodstain pattern types, hair, fiber, glass, and soil present); they photograph the overall scene in systematic overlapping coverage and produce a rough field sketch with a north arrow and scale · Evidence prioritization and processing: students create a written evidence recovery plan listing the order in which items will be collected and why, then execute the plan—collecting, packaging, and labeling each item with a unique item number and completing a chain-of-custody log entry for each · Pattern narrative: after collection, students write a scene narrative describing each bloodstain pattern category identified, the corresponding collection or documentation action taken, and any preliminary interpretive statement that is supportable by the physical evidence
Materials: Mock indoor scene setup (simulated blood patterns, planted hair and fiber, glass fragments, soil sample, paint smear), full PPE for each student, camera, measuring tape, field sketch paper, evidence bags and packaging materials (assorted, all paper), item-numbered evidence tags, chain-of-custody log, scene narrative form
Check: Instructor evaluates the complete documentation package using a 20-point rubric: photography coverage (5 pts), sketch accuracy and completeness (5 pts), chain-of-custody log with no gaps (5 pts), and written pattern narrative using correct terminology without unsupported conclusions (5 pts); minimum passing score is 14 of 20

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.

Crime scene processing and documentation
1. During the initial walk-through of a mock scene, what is the primary purpose of the walk-through?
Evidence collection and preservation
2. A technician collects a hair sample but packages it in a sealed plastic bag and closes it immediately without air-drying. What is the most significant risk of this packaging choice?
Bloodstain pattern analysis and interpretation
3. Which statement in a scene narrative about a bloodstain pattern is most appropriate and scientifically supportable?
Crime scene documentation
4. What is the correct sequence for photographing a piece of trace evidence?
Evidence recovery and prioritization
5. A technician finds a loose fiber near an open window. According to proper evidence prioritization, when should this fiber be collected relative to a stable bloodstain swab on the baseboard?
Crime scene documentation
6. Which item of information is NOT required on a properly completed field sketch?
Chain of custody and legal standards
7. A chain-of-custody log entry is missing the transfer signature when evidence moved from the collecting technician to the evidence room officer. What is the primary consequence of this gap?
Bloodstain pattern analysis and interpretation
8. During a mock-scene assessment, a student identifies a stain on the floor showing a central void surrounded by radiating satellite drops. Which bloodstain pattern category does this most likely represent?
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