At first glance, forensic photography is merely highly skilled commercial photography focused on recording places, objects and people. When these things begin to include crime scenes, weapons, injuries and other macabre things left behind where something grisly happened, we should probably regard this through a different lens.

To understand the mechanisms of what happened, the relevance of objects related to an event, and therefore the fault of persons involved, needs to be recorded for further study by law enforcement officers, attorneys and eventually judges and juries.

The end results — and accompanying detailed photographs and videos — will eventually be used in a court of law and require a high degree of authenticity. This is usually provided by the photographer both through a chain of custody, both to prove that the evidence has not been tainted, lost, purloined or misused in some way, as well as by direct testimony to verify the images and provide context. This authentication will also be supplemented by testifying experts and officers of the court as they explain how the images tell the tale of what transpired on a fateful night (or day).

Forensic photography, then, is a matter of determining which shots will best tell the story, and then systematically gathering those images, which will range from overall scene views to detailed minute evidence. It requires a skilled forensic photographer with: the right tools; a good eye and an understanding of police protocol; a knack for evidence handling and authenticity (so he or she will be able to determine which images to capture); and the know-how to solve technical problems in order to capture those images, and protect them so they are useful.

Crime scene image gathering does offer some particular challenges that commercial photographers never encounter. The best forensic photographers have come up with techniques that solve those very challenges.

 

Challenge one: the unrepentant serial number

Serial numbers on mechanisms like weapons, vehicles, machinery, medical devices and other property sometimes can be worn, scratched, filed off or even painted over. But because these numbers are generally stamped into metal, the impressions are still there for one who has the insight to look deeper. One method of revealing ghost images of serial numbers requires a little finesse with powdered chalk.

First, remove any grease or debris from the area of the number (after first photographing it in its natural condition). When the area is completely dry, lightly dust it with chalk powder (white on a dark object, or black on a light object for contrast). Use an alcohol wipe straight across the surface to remove the excess dust which was not trapped in the depressions. Don’t scrub. The numbers will stand out in contrast, due to the chalk caught in the depressions. Using a close-up lens and a tripod, vary the lighting to enhance the numbers. A straight down studio light may not be quite as revealing as a light cast from the edge, which makes shadows that add depth and enhance the powdered numbers.

 

Challenge two: blood blowback

Blood spatter, blood drops, pools of blood — for a blood spatter expert, every drop, every patch of blood splashed on walls, furniture, floors and objects can tell a very revealing story. When the photographer is capturing all of the blood evidence, they should not fail to look for blowback or the blood spray that would splash away from a wound and attach to the weapon and the perpetrator. It is a scientific principle that blood will be sucked backwards in the vacuum left by a passing projectile, and sometimes it will be sucked into the bore of the gun itself.

Criminals may wipe a weapon clean (or so they think), but the clever use of a borescope and a 90 degree mirror tube can provide evidence of that spatter inside the gun barrel, which should be photographed and then collected before any other processing is done on the weapon. A caveat: test firing the weapon to get a bullet match will destroy that DNA evidence, so look before you fire. Obviously, look down the barrel only when the weapon has been unloaded and verified.

 

Challenge three: capturing ghost bruises

Not all bruises on a victim will be obvious to the naked eye, so when taking pictures of a victim’s body, assume that there is evidence hidden in plain sight. Once general photos are taken of cuts, bullet wounds and obvious injuries, quickly place a special UV filter (Kodak’s Wratten 18A – about $500 USD, which allows only a wave length of around 400 nano-meters of UV light) over the lens and look again. Long wave UV light penetrates deeper into the skin than ordinary light; therefore, bruises, bite marks and other festering wounds will become clearly obvious and able to be photographed.

Interestingly, tattoos, Mongolian spots and birthmarks go deeper into the skin than UV, so these will not show up. A bruise under a tattoo, therefore, will not be obscured by ink. The other challenge is figuring out where the invisible bruises are; since these bruises are not visible, a series of shots adjacent to each other (called ‘bracketing’) will ensure that the right spot is captured in at least one picture. And maybe something unexpected will show up in a neighbouring shot.

One more tip: be sure to explain that the images are from UV filter, and show natural light images of the same areas for comparison. One doesn’t want to be accused of doctoring evidence when simply photographing through a different light spectrum.

 

Challenge four: a technique from the psychedelic 60’s

Many organic fluids such as cleaned-up blood, semen, urine, saliva and other secretions are invisible when dry. But turn off the room lights, draw the shades and get out your ultraviolet light wand and you will be surprised at what jumps out. Bed sheets, bathrooms, or wherever people have interacted with each other in certain ways will leave traces that glow under the ‘black light’ UV projector. Even a bleached tile floor will glow with a tell-tale image pointing to exactly where blood was spilled. Photographing this evidence is simple, but requires a tripod and a long exposure (bracketing a few f-stops in either direction to be sure). Corroborate the same area with natural light shots as well for comparrison.

 

Challenge five: thinking like a bad guy

At the crime scene, of course, a checklist is critical in order to assure full coverage. After that task is complete, it is advisable for the experienced photographer to stop, look around, use what was just observed and think about what happened. By running a few possible scenarios in his mind, places where evidence could appear will become noticeable: cast off blood on the ceiling; minuscule dart-shaped dings in furniture from a ricochet; or subtle displacement of dust on a bureau where someone may have touched it when stumbling. Wadded-up candy wrappers on top of footprints might lead to fingerprints on a cabinet door where snacks are kept. These possible valuable clues will be long gone after the CSIs pack up and release the scene, so do take a moment to use the most important tool in evidence gathering — the brain.

 

Your Turn: Do you have any unusual tips for photographing obscure or hidden evidence? Seen any tricks on the CSI shows lately? Please tell us more – we’d love to hear from you.

Comments

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4 Responses

  1. Sherwood Botsford

    Closeup photography can reveal details, but it has a very thin zone of focus. One way around this is referred to a focus stack. You take a series of images, moving the camera forward by a fraction of a mm between each image.

    The post processing required may stretch the normal limits allowed for digital image work. The photographer will need to provide *all* the original images, and prints of the individual mask layers that carry the in-focus segment of each image.

    ***

    Edge lighting. Often having the light at a very shallow angle will reveal certain details. But only edges that cast a shadow show up. With the camera on a tripod, take repeated exposures with the light coming from various angles.

    ***

    Acid etch: If all the surface material of a serial number has been filed off, you may be able to reveal by etching the metal with acid. When metal is stamped, distorations in the grain of the metal extend by 1 to 2 times the depth of the stamp into the metal. E.g. If the metal stamps went in 10 thousands of an inch there will be grain pattern distortions another 10-20 thousands of an inch into the metal. This distorted grain changes the speed that the metal dissolves, leaving a subtle pattern.

    Reply
    • Douglas Filter

      Thanks for expanding on our content, Sherwood. You’re absolutely right, the techniques you describe are even more advanced, but very effective. It is obvious that you have both expertise and a talent for explaining technologies. Hats off to you!

      The acid etch process is particularly effective 99.9% of the time, an excellent technique and is best done in a lab. Sounds like you have some good experience doing that as well.

      I have played around with focus stacking, and, while time consuming, the results are stunning. I have, however, made hundreds of closeup and macro photos in the conventional way which, while they may have depth of field limitations on the resulting image, they still worked in court. Explaining the masks and various steps required to get sharpness throughout the depth of the photo can take some valuable time away from whatever message is being promoted at trial, and can be destroyed in cross examination by one question from the other side – “Sir, is this image manipulated in any way” … your answer “Yes sir, but” … “No further questions”.

      However, this is not to say that image stacking would not become more mainstream in the future. I was able to redefine Apple’s QT VR virtual Reality technology and use it in a case in the US (“Lewis v Colorado Rockies Baseball Club” 95CV2718 Colorado Civil Proceedings, 1995) and use it successfully to provide a virtual tour of the public areas around the stadium. It was a trial to the bench, in other words, only a Judge and no jury, and the Judge was both interested in technology and able to understand the process. Here’s a link: http://bit.ly/1CBPrcc

      Thanks for your valuable contributions, Sherwood. We look forward to hearing from you again.

      Reply
    • Jasmin Sobeih

      My name is Jasmin, and I love this site. My main goal in life is to become a forensic journalist. I am currently studying Broadcast journalism, but I don’t really want a carer in TV. I would like to know after I have done my BA in journalism, I would like to know what steps to take next to progress into Forensics.

      I watch snapped and SCI, and love those shows. I have always wanted to do Forensics ever since I was young. If, you could give me some advice that would be good. I love this site
      Many regards from Jasmin

      Reply
  2. Robert Bond

    I work for a community college and we are setting up a forensics photography course. I have been charged with buying a filter to be used with Blue Star(?) blood photography. I am not a photographer – just a picture taker – LOL. We have a D3300 Nikon I purchased for instructional purposes. What filter should I buy to show up blood in photos using Blue Star ?

    Reply

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