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newSchoolWorks.com › VoTechWorks › Agriculture, Environment & Public Service › Crime Scene / Forensic Technician › Capstone Project: Integrated Crime Scene Investigation › Lesson 2
AGR-CSI53-09 · Lesson 2 · 80 clock hours · lab

Scene Execution: Documentation, Evidence Collection, and Latent Print Processing

Objective. Working individually under real-time instructor observation, the student will process a simulated indoor crime scene — completing systematic photography, sketching, evidence mapping, packaging, and chain-of-custody paperwork, plus latent print detection and lifting on at least four different substrate types — within the time limit and with no critical procedural errors as defined by the IAI CCSI and Latent Print exam domains.

⚠ 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.

VoTechWorks program approval and accreditation are still in progress. Credentials are issued only by the certifying bodies named in each program, after their own exams.

Scene Execution: Documentation, Evidence Collection, and Latent Print Processing

This capstone lab session brings together every skill you have built during the program. You will process a complete simulated indoor crime scene — alone, in real time, under instructor observation — producing a case file that could stand up in court. The standard is not "good effort"; it is procedural correctness, because the IAI CCSI and Latent Print certification exams, and your future employer, demand exactly that.

Safety First: PPE and Scene Hazards

Before you touch anything, suit up completely. Nitrile gloves protect you from bloodborne pathogens and prevent you from depositing your own ridge detail on surfaces. Tyvek suits keep trace evidence off your clothing and prevent fiber transfer. Eye protection is mandatory whenever you are working with fingerprint powders, cyanoacrylate fumes, or the alternate light source (ALS). Wear your N95 respirator during any powdering operation and throughout cyanoacrylate fuming — cyanoacrylate vapors are a respiratory irritant and the fuming chamber must be used only in the designated ventilated area with the lid sealed. Never bypass the chamber's ventilation interlock. If you detect fumes outside the chamber, stop, alert the instructor, and evacuate the immediate area. Intentional contamination hazards have been planted in each scene; treat every unknown substance as potentially biohazardous.

Scene Security and the Preliminary Walk-Through

Your first act at the scene boundary is to complete the scene security log: record your name, the date and time, your entry point, and the condition of the scene as you found it. Sign it. This document is the first link in chain of custody. Next, conduct a slow, hands-off walk-through to identify the scene boundaries, note item locations, and flag safety hazards. Do not move, touch, or collect anything yet. Use this pass to plan your photographic sequence.

Systematic Photography

Forensic photography follows an overall-to-specific sequence. Begin with overall (establishing) shots that show the full room and all four walls. Move to mid-range shots that place individual items of evidence in context. Finish with close-up shots — one without a scale and one with a ruler or ABFO scale in frame — for every item and every area of interest, including the simulated bloodstain. Record every exposure in your photographic log: frame number, direction, distance, aperture, shutter speed, ISO, flash use, and a brief description of what is depicted. A photograph you cannot describe and authenticate in court is worthless.

Sketching and Measurement

Your hand-drawn sketch must include: a north arrow or direction reference, the room dimensions, the location of all fixed reference points (doors, windows, outlets), the position of every evidence item referenced by item number, a scale or written disclaimer, a legend, and your signature with date and time. Use the rectangular-coordinate or triangulation method to fix each item's position from two fixed reference points. Measurements must be accurate to within ± 6 inches — use a metal tape measure, not a cloth one that stretches. After the lab, digitize your sketch in the program's CAD/diagramming software, entering the same measurements. The two versions must match; discrepancies indicate a field-notes error that must be explained in writing.

Evidence Logging and Chain of Custody

Assign each item a sequential evidence number before you collect it. Record in the evidence log: item number, description, exact location (coordinate or triangulation reading), collection method, packaging type, and your initials. Complete a chain-of-custody form for every single item — no exceptions. The chain of custody documents every person who handles the item from collection through storage. A broken chain can cause evidence to be suppressed in court. Seal each package with tamper-evident tape, initial the seal across the flap, and record the seal number. Package biological material in paper (never sealed plastic, which accelerates degradation). Package dry trace evidence in bindles placed inside paper envelopes. Package items that might cross-contaminate each other separately.

Latent Print Development: Technique Selection

Choose your development technique based on the substrate and whether the print is fresh or aged. On non-porous smooth surfaces such as glass and polished plastic, start with fingerprint powder (black powder on light surfaces, white or aluminum powder on dark surfaces, magnetic powder where appropriate). On semi-porous surfaces such as cardboard, cyanoacrylate (superglue) fuming develops the print first; follow with powder or fluorescent dye if needed. On porous surfaces such as unfinished wood, chemical methods such as ninhydrin or physical developer are standard, though the ALS may reveal fluorescent deposits first. In this lab you will use at minimum fingerprint powder and cyanoacrylate fuming. After development, photograph every developed print in place (with and without scale), then lift with appropriate tape or gelatin lifter, mount the lift on a backing card, and label it: item number, substrate, technique used, date, time, your name, and orientation arrow.

Latent Print Comparison Using ACE Methodology

ACE stands for Analysis, Comparison, Evaluation. In the Analysis phase, examine the latent print alone: assess quality, ridge flow, and the specific friction ridge details (minutiae) you can clearly see. Note areas of clarity and distortion. In the Comparison phase, place the latent alongside the exemplar and systematically compare corresponding areas, noting agreements and differences in minutiae type and relative position. In the Evaluation phase, reach a conclusion: Identification (the prints share the same source and there are no unexplained differences), Exclusion (the prints have different sources), or Inconclusive (quality or completeness is insufficient to support either conclusion). Write your rationale citing specific ridge details — ridge endings, bifurcations, dots, short ridges — by location. Vague conclusions without written support will not pass the IAI Latent Print exam or this exercise.

Connecting to Your Credentials

Every task in this lab maps to a domain tested by the IAI CCSI exam (scene documentation, evidence handling, safety) or the IAI Latent Print certification exam (substrate-appropriate processing, comparison methodology, documentation). Execute each step as if the examiner is watching — because in this lab, they are.

Key terms10

Chain of CustodyA continuous, documented record of every person who has collected, handled, transferred, or examined a piece of evidence, from the moment of collection through its final disposition; a break in this record can render evidence inadmissible.
Overall-to-Specific Photographic SequenceA structured forensic photography approach that begins with wide establishing shots, progresses to mid-range contextual shots, and ends with close-up detail shots (with and without scale) for each item of evidence.
Rectangular-Coordinate MethodA crime scene measurement technique in which an item's location is fixed by measuring its perpendicular distances from two intersecting baseline walls or reference lines, producing an X/Y coordinate pair.
Cyanoacrylate FumingA latent print development technique in which superglue vapors react with amino acids, fatty acids, and proteins in eccrine sweat residue, forming a white polymer deposit that reveals ridge detail on non-porous and semi-porous surfaces.
ACE MethodologyThe three-phase latent print comparison process — Analysis (examine the latent alone), Comparison (systematically compare latent and exemplar side by side), Evaluation (render a conclusion of Identification, Exclusion, or Inconclusive) — required by OSAC/SWGFAST standards and tested on the IAI Latent Print certification exam.
SubstrateThe surface on which a latent print is deposited; classified as porous (e.g., unfinished wood, paper), non-porous (e.g., glass, polished plastic), or semi-porous (e.g., cardboard, glossy paper), with technique selection driven by substrate type.
Gelatin LifterA flexible, adhesive sheet made of gelatin used to lift developed latent prints — and sometimes footwear impressions — from textured or curved surfaces where conventional tape lifts would distort or fail.
Friction Ridge MinutiaeThe individual ridge detail characteristics used in latent print comparison, including ridge endings, bifurcations (forks), dots, short ridges (islands), and enclosures; the presence, type, and relative position of minutiae form the basis of an identification or exclusion.
Tamper-Evident SealAn adhesive tape or label applied across a sealed evidence package that shows visible damage if the package is opened; the technician must initial the seal across the closure so any tampering is immediately apparent.
OSAC/SWGFAST StandardsPublished guidelines from the Organization of Scientific Area Committees (OSAC) and its predecessor, the Scientific Working Group for Friction Ridge Analysis, Study and Technology (SWGFAST), that define best practices for latent print processing, documentation, and comparison in the United States.

Worked examples4

1. You are sketching a rectangular room that measures 14 feet 6 inches by 11 feet 3 inches. A spent cartridge case (Item 3) is located 3 feet 4 inches from the south wall and 5 feet 9 inches from the west wall using the rectangular-coordinate method. Convert all measurements to decimal feet and record them as you would in your evidence log.
  1. Step 1 — Convert room length: 14 feet 6 inches = 14 + (6 ÷ 12) = 14 + 0.50 = 14.50 ft.
  2. Step 2 — Convert room width: 11 feet 3 inches = 11 + (3 ÷ 12) = 11 + 0.25 = 11.25 ft.
  3. Step 3 — Convert Item 3 south-wall distance: 3 feet 4 inches = 3 + (4 ÷ 12) = 3 + 0.333... ≈ 3.33 ft.
  4. Step 4 — Convert Item 3 west-wall distance: 5 feet 9 inches = 5 + (9 ÷ 12) = 5 + 0.75 = 5.75 ft.
  5. Step 5 — Record in evidence log: 'Item 3 — spent cartridge case — Location: 3.33 ft from south wall, 5.75 ft from west wall (rectangular coordinate); Room: 14.50 ft (E-W) × 11.25 ft (N-S).'
Answer: Room is 14.50 ft × 11.25 ft. Item 3 is at coordinates 3.33 ft (from south wall) × 5.75 ft (from west wall). These values must appear on both the hand-drawn sketch and the digitized CAD version; any difference greater than ± 6 inches (0.50 ft) requires a written explanation.
2. Your sketch shows Item 7 at 8 feet 2 inches from the north wall. When you digitize the sketch and scale the CAD drawing, the software places Item 7 at 8 feet 9 inches from the north wall. Determine whether this discrepancy exceeds the allowed tolerance and state what action is required.
  1. Step 1 — Convert the hand-drawn measurement to decimal feet: 8 ft 2 in = 8 + (2 ÷ 12) = 8 + 0.167 ≈ 8.17 ft.
  2. Step 2 — Convert the CAD measurement to decimal feet: 8 ft 9 in = 8 + (9 ÷ 12) = 8 + 0.75 = 8.75 ft.
  3. Step 3 — Calculate the discrepancy: 8.75 − 8.17 = 0.58 ft.
  4. Step 4 — Convert discrepancy to inches for comparison with tolerance: 0.58 ft × 12 = 6.96 inches.
  5. Step 5 — Compare to allowed tolerance of ± 6 inches (0.50 ft): 6.96 inches > 6.00 inches, so the discrepancy exceeds the tolerance.
Answer: The discrepancy is approximately 6.96 inches, which exceeds the ± 6-inch tolerance. The student must return to field notes, re-examine the original tape measurement, and submit a written explanation documenting which measurement is correct and how the error occurred. The corrected measurement must be updated in whichever version (sketch or CAD) contained the error before the case file is submitted.
3. You are processing a scene with four substrate types: (A) a drinking glass, (B) a piece of glossy cardboard packaging, (C) an unfinished wooden shelf, and (D) a smooth painted metal door handle. You must select at least two development techniques across these four substrates. List the most appropriate primary technique for each substrate and explain your selection.
  1. Step 1 — Classify each substrate: Glass (A) = non-porous smooth; Glossy cardboard (B) = semi-porous; Unfinished wood (C) = porous rough; Painted metal door handle (D) = non-porous smooth.
  2. Step 2 — Select technique for A (glass, non-porous): Fingerprint powder — black or aluminum powder applied with a brush lifts ridge detail well from smooth non-porous surfaces. This counts as Technique 1.
  3. Step 3 — Select technique for B (glossy cardboard, semi-porous): Cyanoacrylate fuming — the semi-porous surface may absorb some residue, but cyanoacrylate reacts with the surface deposit before it soaks in; follow with fluorescent dye or powder if needed. This counts as Technique 2.
  4. Step 4 — Select technique for C (unfinished wood, porous): Chemical development such as ninhydrin (reacts with amino acids in sweat) is standard; the ALS should be used first to identify any fluorescent deposits non-destructively.
  5. Step 5 — Select technique for D (painted metal, non-porous smooth): Fingerprint powder (black or white depending on paint color) is appropriate; magnetic powder may be used if the surface is smooth enough to avoid smearing.
Answer: A — fingerprint powder; B — cyanoacrylate fuming; C — ninhydrin or other amino-acid reagent (with ALS first); D — fingerprint powder. The two mandatory techniques (powder and cyanoacrylate) are covered by substrates A and B respectively, satisfying the lab requirement. Technique selection must be documented in the evidence log with a brief rationale for each substrate.
4. Your photographic log must record the distance from camera to subject for a close-up of Item 2 (a latent print on a glass surface). The camera sensor's field of view at the working distance fills a 4-inch-wide frame. You want the print to fill approximately 75% of the frame width. The print ridge area is estimated at 0.9 inches wide. How wide a frame do you need, and does a 4-inch frame at the current distance satisfy the 75% goal?
  1. Step 1 — Determine the required frame width for the print to fill 75%: If the print (0.9 in) is to equal 75% of the frame width, then frame width = 0.9 ÷ 0.75 = 1.20 inches.
  2. Step 2 — Compare to current frame width: Current frame width = 4 inches. A 4-inch frame would make the 0.9-inch print occupy 0.9 ÷ 4.0 = 0.225, or 22.5% of the frame width.
  3. Step 3 — Conclusion: 22.5% is well below the 75% target. You must move the camera closer or use a macro lens setting to narrow the field of view to approximately 1.20 inches.
  4. Step 4 — Record the working distance and settings that achieve the 1.20-inch frame in the photographic log, along with scale bar placement confirmation.
Answer: A 4-inch-wide frame places the print at only 22.5% of frame width, far below the 75% goal. The camera must be repositioned or the zoom/macro adjusted until the field of view is approximately 1.20 inches wide, at which point the 0.9-inch print will fill 75% of the frame. Log the final distance and settings; include one shot with the ABFO scale in frame.

The math in this lesson1

Learners convert feet-and-inches room and evidence measurements to decimal feet for the evidence log.
N-Q.1
Brush up in the math halls at newSchoolWorks.com:
In class: Instructors prepare three distinct simulated scenes (one active per student group rotation) staged in the program lab with planted evidence items, latent prints on varied substrates (glass, cardboard, painted wood, and plastic), a simulated bloodstain area, and intentional scene-contamination hazards; each student independently processes their assigned scene over two lab sessions, completing: a scene security log, an overall-to-specific photographic sequence with exposure log, a hand-drawn sketch with measurements and a legend, an evidence log with item numbers, collection method, and packaging notation, chain-of-custody forms for every item, and latent print processing using at minimum two development techniques (e.g., fingerprint powder, cyanoacrylate fuming) appropriate to each substrate, with lifts mounted and labeled per IAI standards. · Students digitize their hand-drawn sketch using free CAD or diagramming software introduced in Course 2 (e.g., Dia or the program's licensed option), cross-checking all measurements against their field notes; they submit both the hand-drawn original and the digital version as part of their case file, allowing instructors to verify measurement accuracy and documentation consistency. · After scene processing, each student completes a blind latent print comparison exercise: they receive five latent lift cards from their own processing and five unknown exemplar cards and must use ACE (analysis, comparison, evaluation) methodology to render a written conclusion (identification, exclusion, or inconclusive) for each pair, citing specific ridge detail observations — this exercise maps directly to IAI Latent Print certification exam competencies in comparison methodology.
Materials: Simulated crime scene lab with staged evidence; fingerprint powder kit (black, white, magnetic); cyanoacrylate fuming chamber; gelatin lifters; lifting tape and backing cards; UV/alternate light source (ALS); numbered evidence placards and flags; evidence packaging (paper bags, plastic bags, boxes, bindles); tamper-evident tape and evidence seals; chain-of-custody forms; photographic log forms; 35mm-equivalent DSLR cameras (program-supplied) and tripods; measuring tapes, rulers, and protractors; graph paper and drafting pencils; CAD/diagramming software workstations; latent print comparison worksheets; nitrile gloves, Tyvek suits, eye protection, N95 respirators; reference: current SWGFAST/OSAC latent print processing guidelines; IAI CCSI and Latent Print candidate handbooks
Check: Scene processing evaluated by instructor using a 100-point Critical Task Checklist: photography sequence and exposure log (20 pts), sketch accuracy ± 6 inches on all measurements (15 pts), evidence log completeness with no unbroken chain-of-custody (20 pts), latent print technique selection appropriateness for each substrate (15 pts), lift quality and labeling (15 pts), PPE compliance throughout (15 pts). Minimum passing score: 80/100 with a score of zero on any PPE or chain-of-custody critical item requiring immediate remediation before the student may continue. Latent comparison exercise: at least 4 of 5 pairs rendered with a correct conclusion and written ridge-detail rationale (80% pass).

Practice check8

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

IAI CCSI — Evidence Collection and Packaging
1. A student collects a moist blood swab from a simulated scene and seals it immediately in a plastic zip-lock bag. What critical error has the student made?
IAI Latent Print Certification — Comparison Methodology
2. During the ACE latent print comparison exercise, you identify three ridge endings and two bifurcations in the latent that correspond in type and relative position to the exemplar, but one ridge appears to split in the latent where the exemplar shows a continuous ridge. What is the most appropriate conclusion under ACE methodology?
IAI CCSI — Scene Documentation and Photography
3. Which of the following correctly describes the required photographic sequence for a piece of evidence at a crime scene?
IAI CCSI — Safety and PPE; IAI Latent Print — Processing Safety
4. You are fuming a smooth plastic evidence item in the cyanoacrylate chamber. Before you begin, which PPE step is most critical to complete?
IAI CCSI — Scene Documentation and Sketching
5. A student's scene sketch places Item 5 at 9 feet 4 inches from the east wall. The digitized CAD version places it at 9 feet 10 inches from the east wall. Does this discrepancy require corrective action under the lab's ± 6-inch tolerance?
IAI Latent Print Certification — Substrate-Appropriate Technique Selection
6. Which substrate-technique pairing is MOST appropriate as a primary development method according to OSAC/SWGFAST guidelines?
IAI CCSI — Chain of Custody and Evidence Integrity
7. A chain-of-custody form is missing the signature of the officer who transferred Item 9 to the evidence technician. What is the immediate consequence if this error is not corrected before submission?
IAI Latent Print Certification — ACE Methodology and Documentation
8. During the ACE Analysis phase, an examiner notes that a latent print lifted from a plastic bag has significant pressure distortion in the lower third but clear ridge detail in the upper two-thirds. What is the correct action before moving to the Comparison phase?
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