Integrated Scene Simulation: Full Latent-Print Workflow

Integrated Scene Simulation: Full Latent-Print Workflow

This lesson pulls every skill you have built across the course into a single, uninterrupted workflow. In a real crime scene, no instructor will cue you to switch techniques or remind you to photograph before you dust. This simulation holds you to that same standard.

Before You Touch Anything: Scene Approach and Surface Assessment

The first minutes at any scene are the most critical. Enter only after you have donned the correct PPE—nitrile gloves, Tyvek suit, booties, and eye protection. Chemical development agents such as cyanoacrylate (CA) fumes and some fingerprint powders can irritate airways and mucous membranes; if CA fuming will occur inside the scene room, confirm the fuming cabinet is used and the room ventilation is adequate before proceeding.

Complete your surface assessment form before opening a single powder jar. Walk the scene and categorize every surface:

• Porous (paper, cardboard, unfinished wood): absorbs the sweat residue; requires chemical reagents such as ninhydrin, 1,8-diazafluoren-9-one (DFO), or physical developer.
• Non-porous smooth (glass, painted metal, plastic): residue sits on top; powdering or CA fuming is the first-line approach.
• Non-porous rough or textured: fluorescent powder or CA followed by fluorescent staining may outperform standard gray or black powder.
• Wet surfaces: small-particle reagent (SPR) is appropriate.

Document every item number, surface material, expected print type (patent, plastic, or latent), and your planned technique. This form becomes part of your evidence package.

Sequencing: Photography First, Always

Sequence errors destroy evidence permanently. The correct order is rigid:

1. Photograph the undisturbed surface with scale and without scale, using your DSLR and macro lens.

2. Apply the development technique appropriate to that surface.

3. Photograph developed prints immediately—before lifting—using oblique lighting or ALS as needed.

4. Lift using the appropriate tape or gel lifter.

5. Package the lift on a contrasting backing card, seal, and label.

6. Complete the evidence label and chain-of-custody (CoC) form for that item before moving to the next.

Skipping or reordering any step cannot be corrected after the fact.

Technique Selection Reminders

Black powder is most visible on light, smooth surfaces. Gray or white powder is preferred on dark surfaces. Magnetic powder reduces surface abrasion on delicate finishes. CA fuming polymerizes sweat amino acids into a white-to-off-white ridge deposit; it is the method of choice when multiple surfaces of different colors are present in a single enclosed space. After CA development, fluorescent dyes (such as rhodamine 6G or Ardrox) can be applied to enhance prints for ALS examination. When working under the ALS, use the appropriate goggles for the wavelength emitted—this is a safety requirement, not optional.

Lifting, Packaging, and Labeling

Each lift must be labeled before it leaves your hand. A minimum label includes:

• Case number
• Item number
• Date and time collected
• Location description (e.g., "exterior of south-facing window, lower-left pane, approximately 18 in. from floor")
• Collector's name and signature

Seal packaging with tamper-evident tape. Any gap in this record creates a chain-of-custody break that can exclude evidence at trial.

Preliminary ACE-V Comparison Report

Using the two designated prints—a known exemplar and an unknown latent—you will conduct an ACE-V analysis:

• Analysis: Examine the latent alone. Note quality, ridge count, Level 1 pattern (arch, loop, whorl), Level 2 details (minutiae—bifurcations, ridge endings, dots, enclosures), and any Level 3 features visible at the print's quality level.
• Comparison: Place the latent and the exemplar side by side. Align on a common reference point and move systematically through the print.
• Evaluation: Reach one of three conclusions—Identification (ID), Exclusion, or Inconclusive. Document the features that support your conclusion.
• Verification: Your written report must include a statement requesting independent verification by a second examiner. In casework, no identification is reported to stakeholders without that verification step.

Your one-page report should state your conclusion plainly, list the supporting features with their locations, note any limitations (poor quality areas, pressure distortion), and close with the verification request.

Chain-of-Custody and the Automatic Resubmission Rule

CoC forms must be complete and error-free. In this simulation—as in real casework—any error on a CoC form requires you to resubmit a corrected form with a written explanation of the error. Alterations on original forms must be made by single line-through with the corrector's initials and date; white-out or erasure is prohibited.

Passing Standard

You must score at least 16 of 20 points on the rubric to pass this simulation. Reviewers will check that your surface assessment was complete before scene contact, that each technique matches the surface type, that prints show no contamination from incorrect technique order, that every photograph meets the quality checklist, and that your comparison report states a clear, documented conclusion.