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Forensics Fundamentals – Part Two

In Part One of Forensics Fundamentals, I talked about photographic immersion for military personnel and law enforcement officers intending to use the craft within their work routines. For instance, they can use photography while documenting domestic violence cases, arsons, accidents, surveillance operations and crime scene investigation coverage. Granted most institutions have a dedicated photographer whose job is solely forensics photography, but there are instances when an officer must perform multiple duties including documentation.

Crime scene investigators learn how to photograph marks and prints on mirrors. Photo by Stacy Pearsall

After photographic fundamentals are covered in class, and before we begin discussing crime scene documentation, we review the importance of light and its characteristics. I explain light quality, intensity, direction, refraction, diffusion, color temperature and more. I explain and demonstrate a variety of lighting styles for detail/macro photography such as direct lighting, direct reflective lighting, oblique lighting, bounce lighting, diffused lighting, transmitted lighting and axis lighting. All of this information is necessary, so the students may know how light enables them to illuminate scenes and, more importantly, latent evidence they can’t perceive with the naked eye.

I implement various light exercises to help illustrate how flat light conceals fibers, hair, patterns and transparent objects. I show a seemingly mundane box of dirt to the students under the room’s overhead lights. To the naked eye, there doesn’t appear to be anything but dirt. But when lit from the side across the dirt’s surface, also known as oblique lighting, shadows are created to reveal the imprint of a shoe.

A shoe impression is lit at a low angle with an LED light to reveal the shoe’s pattern. Photo by Stacy Pearsall

Next, I place clear glass shards on the carpet without the students’ knowledge. As we walk through the staged crime scene, I ask if there’s any evidence that should be photographed. Initially, the glass is looked over.

Students look for evidence under ambient light conditions. Photo by Stacy Pearsall

I place my Lumimuse LED light on the floor using my Spring Clamp with flash shoe. The directional light creates specular highlights and shadows off the glass shards, thus revealing where the glass pieces are located. Not only does the light identify where the glass shards are located, the light provides enough contrast to lock focus on the transparent object while also showing the dimension of the glass so that it may be captured photographically.

Clear glass on the carpet is invisible to the naked eye; therefore, the use of supplemental light is required to reveal its location. Photo by Stacy Pearsall

Photographing glass presents a multitude of challenges. Chief of which is the aforementioned problem of photographing a transparent item. Light is paramount in these situations. That’s why I spend a lot of time going over lighting solutions with my students to include direct light, light bouncing techniques to diffuse the light, the implementation of scrims to disperse the light and background choices (when situations allow).

A flashlight is used to reveal handprints on a clear glass. Photo by Trish Barini

I demonstrate how angling light through the side, or from behind the glass, can reveal latent finger and handprints. Naturally, the rays of light emitted by the flashlight pass directly through the clean, transparent glass uninhibited. However, the oil left behind by human skin is more translucent, thus causing the light to scatter and become visible to the viewer’s eye – voilà.

With this concept in mind, I transition the instruction to mirrors, and explain that the theory and techniques essentially are the same.

An LED light is used to illuminate a fingerprint on a mirror. Photo by Stacy Pearsall

Unlike fingerprints on glass, mirrors are less forgiving and show these prints more readily to the naked eye. However, that doesn’t mean they’re easier to photograph. Depending on the mirror’s type, manufacturer and age, it may have multiple layers – most have at least two.

A graphic illustration of the layered properties of a mirror. Illustration by Stacy Pearsall

Understanding that a fingerprint on a mirror will actually be on the outer glass is important. Not only will you be photographing a fingerprint on glass, you’ll be photographing its reflection from the silver layer behind too. If the camera is not situated directly in-line with the print on the mirror, a ghosting of the print will be visible.

A fingerprint on a mirror taken from a 45-degree angle to show the print and the print’s reflection behind. Photo by Stacy Pearsall

With that in mind, I suggest students use tripods to photograph any evidence on mirrors, whether fingerprints or not. A tripod provides stability for the shooter, but also provides useful bubble-leveling tools. Once accurate height is established and the tripod level and stable, the back of the camera should be adjusted so it’s parallel with the mirror’s surface. I demonstrate using an inexpensive protractor angle finder from the hardware store to ensure both the mirror and the camera are at the same precise angle. In effect, the same procedure is done in art and copy photography.

Forensics photography students prepare to photograph hand and fingerprints on a mirror. Photo by Trish Barini

With any fine detail work such as photographing fingerprints, it’s best to use a macro lens. Macro lenses permit closer lens-to-subject distance allowing the photographer to get much closer to the subject matter. The tough part about shooting macro photography is often the shallow depth-of-field, which makes fine focusing a challenge. Having the camera on a tripod, and using the Live View: Preview Zoom function I’d mentioned previously in Part One, enables tack-sharp manual focus.

Forensics photography students use macro lenses and tripods to photograph fingerprints on a mirror. Photo by Trish Barini

Using large mirrors with multiple skin oil marks, I have the students line up and practice camera alignment and focus techniques using ambient light only. For the students who do not have a shutter release cables, I ask them to use the Self-Timer mode to reduce any unnecessary camera shake.

 

Once they’ve captured natural light images, I ask them to use their flashlights to illuminate the same hand and fingerprints. To best show how light interacts with mirrors, I have them aim the flashlight’s beam directly at the print and take a picture – repeating the process with the flashlight’s beam directed from the top oblique angle and from the side oblique angle.

Forensics photography students practice photographing fingerprints on mirrors. Photo by Trish Barini
An image of a fingerprint on a mirror using an LED light source. Photo by Stacy Pearsall

After the exercise is complete, I discuss useful tools for photographing reflective surfaces whether in the field or in the lab. For instance, I discuss using typical studio equipment and modifying these pieces for forensics photography purposes.

 

I’ve taken a 6’x7’ collapsible black background and cut a vertical strip down the middle. Down the length of the opening, I adhere hook and loop fasteners so the slit may be opened and closed on-demand and may be as big or as small as I require. Using two background support stands on either side of the background, I can position the background, free standing, in front of the reflective surface and shoot from behind and through the vertical slit, thus reducing unwanted reflections.

A black background system with camera slit modification example. Illustration by Stacy Pearsall

Taking it one step further, I create additional slits on both sides of the camera opening – they too have hook and loop fasteners. These additional openings are used to pass through two Variable Friction Arms that are supported by my camera’s tripod using Super Clamps. Each arm has Hot Shoe Attachments that give me the option of using hotshoe flashes or LED panels such as the Lumimuse. These lights are then positioned at 45-degree angles to the object being photographed for even illumination.

 

Alternatives to the Variable Friction Arms are Flex Arms and Magic Arms. There’s also the Macro Bracket Flash Support system.

A black background system with camera slit modification example. Illustration by Stacy Pearsall

Sometimes photographers need to get your lens super-close to the subject, but the tripod hinders that ability. Solutions include using a Variable Friction Arm with a quick release plate or a two or three section Double Articulated Arm on-hand. Both allow the operator the freedom to move the camera in closer to the subject without the need of moving the tripod legs nearer too. I remind students that the further the camera gets from the support, the less balanced it becomes. Using a counterweight on the tripod may be necessary.

 

Given most operators document scenes singlehandedly, having equipment to help support the photographer during locations shoots is essential. If a photographer needs to bounce a light or two, using a Trigrip Reflector along with a Tripgrip bracket system and light stand provides the operator freedom to move the lights into place and keep their hands free to concentrate on the camera operations. That same set up may be used for Trigrip Diffusers too – two birds, one stone.

I use the Manfrotto Stackable Light Stands because the collapse flat and lock to each other, which saves room. Plus, they’re lightweight and easy to haul around from place to place. Moreover, I use them for multiple purposed such as background and light system support.

I know this sounds like a tremendous amount of equipment to bring on location, but it’s actually very compact and can fit into one rolling case if necessary. I always emphasize that it’s better have it and not need it then need it and not have it.

 

Stay turned for Forensics Fundamentals Part Three where we’ll get into crime scene documentation and so much more.