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Situated Testimony

ADVANCED
📖15 min read

Introduction​

Situated Testimony is a forensic interview technique where a witness interacts with a spatial representation of the scene (a 3D model) to aid their recall. Unlike a static presentation, this is a live performance. The Analyst acts as the "driver," navigating the virtual world in response to the witness's verbal descriptions.

“We find that working with spatial testimony and spatial tools helps witnesses unlock certain parts of their own memory which would otherwise be obscured or lost to trauma,” Levidis says. - https://gijn.org/stories/investigating-pylos-shipwreck/

This requires a specific set of Blender skills: speed, fluidity, and the ability to bring to the screen what the witness is describing without technical friction breaking the flow of the interview.

Fluidity

Navigation must be smooth and intuitive. Technical struggles distract.

POV Accuracy

Quickly establishing a verifiable eye-level view is key for testing visibility claims.

Live Marking

Recording the witness's indications ("I stood here", "The car was there") directly into the 3D space in real-time.

1. The "Driver" Setup​

Before the witness arrives, your interface must be optimized for presentation, not modeling.

Clean the Viewport​

Hide everything that isn't the scene.

  • Disable Overlays: Click the Show Overlays button (top right, two overlapping circles) or press Shift + Alt + Z.
  • Hide UI: Press Ctrl + Space to maximize the viewport.

The "Avatar" Camera​

Don't just float around. Create a dedicated camera representing the witness.

  1. Create a new Camera: Shift + A -> Camera.
  2. Name it CAM_Witness.
  3. In Camera Properties, set Focal Length to 35mm or 50mm (standard human perception approximation).
  4. Lock Camera to View: Press N to open the side panel -> View tab -> Check Camera to View.
    • Why? This allows you to navigate normally while "carrying" the camera with you.

2. Live Navigation Techniques​

The witness will say: "I walked down the hall and turned left." You need to execute this movement instantly.

Walk Navigation (The FPS Mode)​

Orbiting is disorienting for non-3D people. Use Walk Navigation to move like a human.

  • Activate: Shift + ~ (tilde key, usually above Tab).
  • Controls:
    • W / A / S / D: Move forward/left/back/right.
    • Mouse: Look around.
    • Q / E: Move Up / Down.
    • Shift (hold): Move faster.
    • Alt (hold): Move slower.
  • Gravity: While in Walk Mode, press Tab. You will drop to the "floor" (collision geometry). This is excellent for walking up stairs or ramps naturally.

Teleporting (Snap to Selection)​

If the witness says "I was standing by the red car," don't fly there manually.

  1. Select the car (Right Click or Left Click depending on keymap).
  2. Press Numpad . (Period) to Frame Selected.
  3. Analyst Tip: This puts you outside looking at the car. To look from the car, rotate 180 degrees.

3. Establishing Point of View (POV)​

When the witness says "I could see him from where I stood," you must verify this geometrically.

Setting Eye Height​

  1. Select your CAM_Witness.
  2. Press N to open the side panel -> Item tab.
  3. Check the Location Z value.
  4. Manually type the witness's eye height (e.g., 1.6m for an average adult standing, 1.2m for sitting).
    • Note: Ensure your floor is at Z=0.

The "Align Active Camera to View" Trick​

Sometimes you find the perfect angle in the viewport, but your camera is elsewhere.

  • Press Ctrl + Alt + Numpad 0.
  • The active camera instantly snaps to your current viewport position.

4. Managing Visibility (Seeing Through Walls)​

In a 3D model, walls block your view of the interior. You need "X-Ray" vision to manage the scene without deleting geometry.

Clipping Region (The Magic Slice)​

This is the fastest way to isolate a room.

  1. Press Alt + B.
  2. Draw a rectangle around the area you want to see.
  3. Everything else disappears. You have a perfect 3D slice of just that area.
  4. To restore the full scene, press Alt + B again.

Camera Clipping (The Wall Hack)​

If you are backing up into a wall to get a wide shot, the camera might be blocked by the wall geometry.

  1. Select Camera.
  2. Go to Camera Properties -> Lens.
  3. Increase Clip Start (e.g., from 0.1m to 1.0m or more).
  4. The camera will now "ignore" geometry close to it, allowing you to see through the wall behind you.

Boolean Slicing (The Clean Cut)​

For a more permanent or renderable cutaway that doesn't depend on your view angle:

  1. Create a Cutter: Add a Cube (Shift + A -> Mesh -> Cube) and scale it to cover the area you want to hide.
  2. Set Display to Wire: In Object Properties -> Viewport Display, set Display As to Bounds. This lets you see through the cutter.
  3. Apply Modifier: Select the building or room object. Add a Boolean Modifier.
  4. Configure: Set Operation to Difference and select your Cube as the Object.
  5. Move the Cube: Drag the cube around to dynamically slice through the building in real-time.

Quick Hiding​

  • Hide Selected: H
  • Hide Unselected (Isolate): Shift + H
  • Unhide All: Alt + H
  • Local View: / (Numpad Slash) - Isolates the selected object completely.

5. Live Annotation​

The witness points to the screen: "He was standing right there." You need to mark that spot immediately.

The Annotation Tool​

  1. Mark the Spot: Shift + Right Click to place the 3D Cursor exactly where the witness indicates. This acts as an immediate visual anchor.
  2. Draw: Hold D (draw key) and Left Click + Drag to draw around the cursor.
  3. Placement Settings: In the top header (N-Panel -> View -> Annotations), change Placement to Surface.
    • Result: Your lines will stick to the 3D geometry (walls, floors) instead of floating on the screen.

Converting to Evidence​

Annotations are temporary. To make them permanent evidence:

  1. Use the Grease Pencil object instead of the Annotation tool for more permanence.
  2. Or, immediately place a Locator (Empty) at the spot: Shift + Right Click (moves 3D cursor) -> Shift + A -> Empty -> Sphere. Name it POI_Witness_Indication_01.

6. Recording the Re-enactment (Auto-Keying)​

Sometimes the witness describes a path ("I walked from the door to the window"). You can record this movement live as an animation.

Setup​

  1. Enable Auto Keying: Click the "Record" button (circle icon) in the Timeline header (bottom of screen).
  2. Set End Frame: Increase the frame count (e.g., to 5000) so you don't run out of time.

The Performance​

  1. Press Spacebar to start playing the timeline.
  2. Enter Walk Mode (Shift + ~).
  3. "Walk" the path the witness describes.
  4. Because Auto Keying is on, Blender records your camera's position and rotation at every frame.
  5. Press Spacebar to stop.
  6. You now have a replayable animation of the witness's described movement.

Methodology Note: The "Leading" Risk​

Methodology Alert

In a situated testimony, the Analyst has significant power to influence the witness.

  • Do not position the camera where you think they were. Let them guide you.
  • Do not use wide-angle lenses (e.g., 12mm) that distort distance unless matching a specific device. Stick to 35mm-50mm for human vision.
  • Record the Session: Always screen-record the entire Blender session. The "performance" of navigating is part of the evidence chain.

Summary​

Situated Testimony turns Blender into a communication device. Your mastery of these shortcuts determines whether the technology aids the testimony or hinders it.

Key Shortcuts to Memorize:

  • Shift + ~: Walk Mode
  • Alt + B: Clipping Region (Slice)
  • D + Left Click: Draw Annotation
  • Ctrl + Alt + Numpad 0: Snap Camera to View
Last updated on by blender-visual-investigation