Crime Scene Photograph Exam 3

Guide Number

how much light the flash is capable of casting into the scene.

Nikon SB 5000 - Guide number of 34 is

(ISO 100) considered a large Guide Number

Sync Speed

the shutter speed that has the shutter completely open when the flash fires; the entire scene receives light.

Nikon SB 5000 - Default Sync Speed is

1/60

Auto Mode for Flash is

TTL BL

TTL

Through the Lens Metering

BL

Balanced Lighting

When in AUTO mode

the camera controls the flash output.

Notice that as you zoom in and out

the flash adjusts to match the focal length selected.

SB-5000

is a dedicated flash unit

dedicated flash unit

meaning it is controlled by the light meter in the camera body. Controls the amount of light cast onto the scene.

dedicated flash is recommended for…

most crime scene flash photography situations. The built in pop-up flash should not be relied on for crime scene photography – the guide number is constant at 35 and the position is fixed

The sync cord is

an important crime scene photography tool. It provides flexibility to re-position the flash as needed for oblique lighting and hard to reach places

Adjusting Exposure Compensation on the Flash

1) Select TTL-BL and press OK

2) Press Exposure Compensation icon to display meter

3) Use Selector Dial to adjust +/

Built-in Diffuser And Bounce Card

Reduces power of flash by redirecting or diffusing the amount of light produced. Can be used in different combinations.

Bounce Flash

Electronic Flash Reduces power of flash by bouncing light off light-colored walls, ceilings or reflectors. Trial and error process.

The zoom button

allows the flash to be directed towards a point beyond the maximum focal point of a lens if desirable.

use fill-in flash

Whenever lighting conditions include bright sunlit areas and dark shadows, or backlit scenes - ensures both parts of scene properly exposed

Fill Flash Sequence

• AUTO or PROGRAM or MANUAL (set ISO to 100)

• Meter bright part of scene by filling frame with bright area.

• Aim flash at area most needed, using sync cord if necessary.

• Take the photograph.

Fill Flash is necessary in…

harsh sunlight - optional on cloudy days or shadow

Oblique Lighting

Side lighting used to light three dimensional textures and patterns of evidence. Flash Unit or Flashlight are the tools of choice

sync cord

It provides flexibility to re-position the flash as needed for oblique lighting ( side lighting)and hard to reach places.

Side lighting creates…

shadows - necessary to better visualize the 3D aspects of evidence. If hard shadows result, a reflector should be used to soften

Shoe Prints Sequence

• Use ISO 100 and an f-stop of f/11

• Angle the flash at approximately 45° as a starting point.

• Bracket your photos; give the examiner a number of good photos to choose from.

• Take photos from all 4 sides.

• Create a shadow over the entire impression if necessary.

Shoe Prints In Snow & Sand

Use snow powder or snow wax to color the impressions first, then photograph.

Tire Track Photography

Similar to shoe prints, but can be much longer.

Usually no more than 7 ½ feet need be documented.

Break down into 5 x 1 ½ foot segments.

Shoot same as shoe prints with 1” overlap of sections.

Bite Marks

For this, many prefer a flashlight over a flash unit.

• Tripod

• ISO 100 and f/11

• Aperture Priority Mode works well here

• Fan the flashlight during slow shutter releases

macro photography

is not the same as a close up or zoomed in. We use a specialized lens that allows us to capture details at a crime scene such as blood spatter, powder grains or fingerprint ridges.

macro photography is used to identify

• Toolmarks

• Fibers

• Hairs

• Latent prints

Macro Lenses – Required Equipment/Environment

• Standard lens

• Macro Lens

• Competent/Consistent/Stable light source

• Scales

• Tripod (maybe)

Because of narrow DOF…

the camera must be held FPP and very still; a tripod or stabilizer may be necessary.

Alternate light sources allow the technician to

employ a variety of narrow wavelengths of the light spectrum to identify, visualize, and document evidence.

ALS being used to detect

latent prints or enhance prints processed with fluorescent powder.

semen stains, other bodily fluids, fibers, particles and other spilled materials.

Trajectory analysis

Internal Ballistics

External ballistics

Terminal ballistics

Internal ballistics

Firearms-toolmarks examiner - Determines where the projectile came from.

External Ballistics

Crime Scene Technicans - Determines the path of projectile.

Terminal Ballistics

M.E. - Determines what the projectile did when it arrived at it’s destination.

Trajectory Analysis

• Wood/Metal rods

• Lasers

• Faro/Laser imaging

Wooden Rods are

old school - warp over time. limited by length

Metal Rods are

old school. Limited by length

Crime Scene Techs can use lasers to

establish the path of a bullet through a crime scene

Preferred laser color

Green - it’s more visible than red

fogging/ mist method

Fog or water mist is introduced to the scene to make the beam of the laser visible.

Card method

In a technique similar to paint with light but without flash units, a tech walks a white card across the scene keeping the laser point on the card the entire time, capturing the laser’s path.

FARO - 3D Imaging & Measurement

• Laser scanner placed on tripod

• Replacing laser trajectory

• Provides a 3D image of the scene

• Provides both video and still images

• Time consuming – can take hours to scan an entire house/structure/area of concern

the most important tool the crime scene technician uses

clean white light

Flash recycle time

the time it takes the flash after exposure to power up and be ready to fire again. The more energy used, the longer it takes.