In the early morning hours of March 5, 2008, twenty-two-year-old Eve Marie Carson, student body president of the University of North Carolina, was shot to death 1 mile (1.6km) from the university campus. According to investigators, the gunman probably did not even know the name of the pretty young woman he gunned down. He then stole her sportutility vehicle and her bank card and sped to an automatic teller machine (ATM) and withdrew cash. ATMs have security cameras, though, and police quickly retrieved a black-and-white photo of the man who used her bank card. He was clearly wearing a Houston Astros baseball cap, and police believed they now knew the face of the man who had killed Carson. But the surveillance footage held more information than police first realized.
For decades, cameras have operated almost like undercover members of a worldwide police force. Surveillance and security cameras keep a watchful eye on banks, parking lots, and stores, and fast-thinking witnesses often have the chance to use personal cameras to record crimes in progress. The assassination of President John F. Kennedy on November 22, 1963, was captured on film by a sightseeing cameraman and became one of the most famous examples of videotaped crime footage in history.
A photograph has been the turning point in many police investigations, because cameras are honest. Unlike eyewitnesses, they do not have emotional slips of memory or recall the wrong details. The person taking the picture, on
the other hand, might not be making an honest record of events, and the person who tries to make sense of the picture might be mistaken when deciding what the photo shows. Investigators often need the help of forensic image experts, people who can professionally assess a picture to decide how honestly a photograph represents the crime. “The camera never
Forensic image experts are often asked to help investigators clear up a poor-quality photograph so they can see details better. Using a computer, forensic image experts generally follow these steps:
1 The image is scanned into the computer and uploaded into a photo editing software program. The program is set to keep track of all changes to the image.
2 The image is enlarged to a size that makes it easier to see.
3 Any lighting problems in the photograph are fixed. This may involve lightening areas that are in shadow or darkening areas that show too much glare.
4 Necessary changes to color are made by adding color to a black-and-white image or using color filters to block out certain background colors that make parts of the image hard to see.
5 The number of pixels per square inch is increased if the photo is blurry or if there are lines or pieces of writing that need to be seen more clearly.
6 The image is then separated into layers. Certain layers that need to be seen by themselves are pulled out of the image and placed against a clear background.
7 A permanent record of the changes made to the image is created, which includes what the changes showed that was not visible in the original image.
lies,” says Geoffrey Oxlee of the Kalagate Imagery Bureau in England. “It merely records what it sees, but this is only useful if the imagery recorded is properly and correctly interpreted.”42
A forensic image expert works in a law enforcement laboratory or as a freelance contractor to develop, process, and enhance photographs used in investigations. The forensic image expert may be asked to process photos from crime scenes and autopsies and may also enhance images in various ways to make them more useful for investigations. The forensic image expert is responsible for keeping detailed records of images and what has been done to them.
Forensic image experts usually need a minimum of one semester of college-level coursework in photography and digital imaging.
Most positions require two years of photography-related work experience in the field of forensics. Some police departments provide on-the-job training.
Forensic image experts must have strong knowledge of photography equipment and software and must be organized. The ability to learn new software is essential because technology in this field changes rapidly. Public speaking skills are also important, as they may be asked to testify in court.
$10,000 to $50,000 per year
Photo evidence has become more common with the prevalence of security cameras and camera cell phones, but rarely is this footage high quality. Surveillance camera photos are often fuzzy and many times fail to capture the one angle that shows the suspects’ faces. Witnesses may be running while taking pictures, producing blurry, shaky photos, often of people’s backs instead of their faces. And since many crimes happen at night, photos may simply be too dark to be of much value. Still, there are ways to make even poor photo evidence potentially useful. Forensic image experts are the people who specialize in making bad photos look better.
The photograph of the man using Eve Carson’s bank card made him the lead suspect in her murder. The ATM image also showed that he was driving what appeared to be an SUV the same color as Carson’s missing Toyota Highlander. An important clue would have been overlooked, however, if investigators had not taken the ATM footage to a forensic image expert. The enhanced image showed something police had not noticed before—there was a passenger in the vehicle’s back seat. The original black-and-white image had not provided enough contrast to reveal him, but the enhanced image added color to the picture that brought the passenger into view. Without the forensic image expert’s help, police might never have known there were two people possibly involved in the crime.
According to Herbert L. Blitzer and Jack Jacobia, who manage the Institute for Forensic Imaging in Indianapolis, Indiana, simple changes to a photograph can be the key to solving a crime. “Small details within an image that might not appear important when first encountered may later be discovered to be crucial to the investigation,” they say. “By capturing details in a photograph they are not only preserved, but their characteristics may also be examined more carefully and in a way that permits them to be placed within the context of a broader investigation.”43
Image enhancement has a long history, and most often, experts at enhancing images use their skills to fix or improve bad photographs for private citizens. Image experts rescue overexposed wedding photos, preserve antique portraits of ancestors, and airbrush the faces of cover models for magazines. However, police departments, too, sometimes seek out the
services of these experts when they need help brightening, sharpening, angling, or magnifying a snapshot that could be important evidence of a crime. In the digital age, there is little that an experienced image expert cannot do to an image.
The last day of 2006 was the last day of George Azarian’s life. The disabled sixty-one-year-old was crossing a street in Revere, Massachusetts, when he was struck and killed by a car, and the driver sped away without stopping. No one came forward to say they had seen the crime. “Investigators had little to go on,” says Megan Woolhouse, a reporter for the Boston Globe, “except for some grainy video from a security camera.”44
The security camera was on the roof of a nearby building, and it was the only witness to the hit-and-run. The camera’s footage showed that a light-colored, sedan-style car hit Azarian and then drove away, but this was not enough to help police track down the right vehicle and culprit. They took the footage to a film enhancement expert who was able to sharpen the image. Although the car’s license plate number was still too blurry to read, the make and model of the vehicle became clear: It was a silver Dodge Intrepid. Police officers pulled records of all the owners of Dodge Intrepids in the area and eventually tracked down the one that killed Azarian.
The photo enhancement that solved this case was nothing fancy—the expert simply sharpened a poor-quality image from a standard surveillance camera. It was, however, enough to solve a case that might otherwise have gone cold. Most examples of image enhancement are just this simple. Forensic image experts do as little as possible to photos or footage, because they know they may be holding the single clue available in a case as well as an important piece of evidence that could be used in a court of law.
“The morality of retouching becomes tenuous when dealing with real events,” says Gwen Lute, author of Photo Retouching with Adobe Photoshop. Image experts, she explains, must be careful not to misuse their knowledge and tamper with photo evidence. “A retoucher must be careful not to be drawn into illegal activity, such as manipulating a picture for a court case or an insurance settlement.”45
An important rule for forensic image experts is to keep their adjustments as simple as they can. In fact, they often use the very same processes and programs available to amateur photographers using any home computer. “The truth is, most
From the moment anyone walks through a casino’s door in Las Vegas, Nevada, a man upstairs is watching. So are all the casino surveillance teams in town. Thousands of cameras record faces in every major gambling place in the city. A surveillance team sits in a special room watching dozens of television screens, all looking for suspicious activity, such as signs of cheating on the game floor.
Surveillance is big business in Las Vegas. Casinos invest in the best technology available. They even have facial recognition software to quickly compare the face of one suspected cheater to the casino’s database of photos of known cheaters. Casinos also link their photograph databases, so a cheater at one place will be just as quickly recognized when he moves across the street to another place.
The gambling industry is the champion in this kind of technology. Even the military and the FBI turn to casinos for new ways to track bad guys.
of the time it is not necessary to do any fancy adjustments,”46 say Blitzer and Jacobia. Most images just need slight clarification, and in forensics, the more basic the adjustments made to a picture, the better. Just because a computer can make certain changes to a photo does not mean the forensic image expert should. If the photo is later questioned in court, the forensic image expert will need to prove not only what was done to a photo but also how and why.
For this reason, forensic image experts often use familiar computer software, like Adobe Photoshop, to do their work. “It is a program that is widely accepted throughout the imaging world and has already been tested in a few court cases,”47 say Blitzer and Jacobia. “This does not mean that what you do to an image in Adobe Photoshop won’t be questioned.” There is a fine line, they explain, “between enhancement and manipulation of an image.”48
Forensic image experts must keep careful records of all the changes they make to a picture, in case they are asked to prove that they did not tamper with its content. Because they must also be able to tell the court why they made the changes, forensic image experts use software that allows them to track these changes. This provides a valuable record of the steps taken in enhancing a photo. With the change-tracking feature turned on, the forensic image expert can get to work.
Before doing anything to an image, the forensic image expert must upload it into a software program. If the image is digital, this may be as simple as inserting a memory card or a disk into the computer. If it is a two-dimensional image, it must first
The same technology NASA (National Aeronautics and Space Administration) has used for years to study storm patterns on satellite video also helps put criminals behind bars. A program called VISAR—which stands for Video Image Stabilization and Registration—helps level out shaky video, clarify blurred pictures of moving objects, and sharpen up still images. In the hands of police departments, this technology means that troubles with nighttime photographs, jittery camcorder footage, and foggy surveillance camera stills are quickly fading into crime-fighting history.
VISAR technology is showing up in many situations. Footage recorded by cameras mounted on police cruisers can be sharpened to reveal license plate numbers and other helpful details. Footage of crimes, recorded by witnesses, can show details that would have been missed before VISAR. Even the military uses VISAR to clear up reconnaissance footage recorded from tanks or helicopters during military operations.
More surveillance cameras are in use than ever before, and cellphone cameras mean that almost anyone could catch a snapshot of a crime in progress. Paired with NASA’s foolproof ways to touch them up, these pictures could mean fewer criminals will get away with their crimes.
be scanned to convert it into a digital file format. Either way, one of the first things done to enhance an image is to change its size.
In digital photography, size has two meanings: the actual dimensions of the photo (its length and width) and the size of the digital file that contains the image. Both kinds of size are important. The photo itself may need to be made larger so that investigators can see details too small to have been seen in the original version—for example, a label on a suspect’s clothing or a bumper sticker on a car. Any time a photo gets larger, however, so must the file size. That is, the number of pixels in the image must also be increased. Pixels are the tiny bits, or dots, that make up any picture. An image with few pixels will not have much detail, because the dots that make up the picture are so spread out that the image is fuzzy. A picture with many pixels, packed closely together, is sharper, more colorful, and a better image overall.
A good way to think of pixels is to imagine a shoebox filled with marbles. If you shake the shoebox, the marbles will not move much. But if you were to stretch the shoebox and make it twice as big, the same number of marbles would move around a lot. You would need more marbles to fill the bigger box. Digital photographs work much the same way. Stretching the picture will spread out the pixels, making the image blurry. Adding more pixels to the bigger image is the only way to keep a larger picture as sharp as the smaller original. Therefore, image enhancement experts always pay close attention not only
to the size of the image but also to the number of pixels per square inch that it contains.
Blitzer and Jacobia say that keeping the same ratio of pixels to image size (the same number of pixels per square inch of the photo) is important to a forensic investigation. When the number of pixels per square inch does not change, they explain, “we have not changed any information in the image.”49
Once an image has been sized, the forensic image expert uses a range of tools in the software program to do different things to the picture, depending on what investigators need to see. There are tools to brighten a dim photo or to darken one that is too bright, and these are helpful if an object is in shadow, for example, or if a face is reflected in a window but glare from the sun makes it too hard to see. There are also tools to sharpen the edges of different objects in a photograph, such as blurry shots of license plates or street signs.
Forensic image experts can even break a photograph into different layers—what is in the foreground and the background of the image—and pull out just one layer or piece of an image that investigators want to see. “One of the great additions for us in forensics is the enhanced layer control,” say Blitzer and Jacobia. “New layer design features allow you to apply editable gradients, patterns, and solid colors, as well as color adjustments, to other layers.”50 Forensic image experts often take advantage of layering to see things such as fingerprints. The ability to pull forward and darken the fingerprint layer while lightening the background layer can make an otherwise useless fingerprint visible enough to help solve a case.
Paper evidence, such as bank checks and handwritten notes, is a common item forensic image experts are asked help to make clear. Joe Nickell, in his book Detecting Forgery: Forensic Investigation of Documents, says investigators often turn to forensic image experts for help studying everything from charred bank bonds to letters written on colored paper. “One use is to enhance writing,” he says, and describes an example of a green registration form with writing too faint to be readable. He says a forensic image expert could use a green color filter to subtract the background color. “The form would thus appear white rather than gray,” he says, “and the writing would consequently be more legible.”51
For many criminal cases, forensic image experts work this kind of magic on a poor-quality photo and point investigators to a suspect. It is likely, however, that a forensic image expert’s work will be questioned in court. “Because crime scene images are frequently critical to a case, they are frequently challenged,”52 says Edward M. Robinson in his book Crime Scene Photography. Digitally enhanced images are closely studied by lawyers and juries. After all, computer software programs can realistically replace one face with another in a family reunion photo, so the same technology could be applied to wrongly accuse a suspect. Marilyn T. Miller of Virginia Commonwealth University says that “disadvantages in using digital image technology center on issues of court admissibility because of easy image manipulation.”53 Therefore, before any suspect is identified from a photograph, investigators turn to one more kind of expert, someone who can testify in court as to whether the person in the photograph and the suspect himself are one and the same.
No two people look exactly alike. Even identical twins have enough differences between their faces that their families and close friends can usually tell them apart. On camera, however, it is much harder to tell one face from another—not just for identical twins but for pictures of any two people who look alike.
Courts and juries must decide whether someone is guilty or innocent. They prefer fingerprints and DNA, forms of identification that point to only one person on Earth. Fingerprints and DNA are considered solid evidence in trials because they remove doubt from a case. This is not true of photographs of people’s faces. Proving that two photographs show the face of one and only one person is very hard to do. A few shadows in a photograph comparison can easily cast a shadow of doubt on the whole case.
To convince a jury that two photos show the same person, it takes an imagery analyst, an expert in scientifically comparing the images in photographs to decide whether they are the same. This is never an easy task, especially since the only photos investigators have of a suspect may be of terrible quality. Still, cameras do not lie. “A professional cameraman using a combination of unusual angles or harsh lighting could record a photograph of a man in such a way that his next of kin would fail to recognize him,” says Oxlee. “Nonetheless, the photograph is still a true image of that man.”54 It is up to the imagery analyst to prove this in court.
Imagery analysts know a great deal about photography, physics, and chemistry, as well as computers, digital systems, light spectrums, and geometry. They also specialize in the biology of human faces, culture, and expressions. They use all of this knowledge when deciding whether two photos are of the same face. To hold up in court, a positive identification must come from a qualified expert who supports his claims with as many scientific facts as possible.
“Few people like to be wrong,” says Oxlee. “Their minds have a tendency to look for features on the imagery to prove that they were correct and to discount cues that suggest otherwise. In other words, they make the facts fit the case.”55 Oxlee says he does the opposite when he analyzes imagery. Instead of finding similarities, he looks closely for ways that two pictures are different. “It takes only one clear difference to enable the analyst to conclude that the persons are not the same,” he says. “However, several clear similarities do not prove that they are the same, as many others may share these similarities.”56
Instead of trying to prove that two pictures are of the same person, imagery analysts try to prove that two pictures are of two different people. They do this with various methods of facial mapping, or the comparison of faces from photographed images. One technique of facial mapping uses computer graphics programs to make both images the exact same size, then rotate them so they are at the same angle (such as head-on or profile). Then one image can be placed on top of the other to see how closely they line up. This method is called superimposing. Another method is to take measurements of different points on both faces and compare them. Common measurements are the distance between the eyes and the width of the mouth from corner to corner. Many points like these are measured on both faces, then compared. If even one major difference is discovered, the faces are not the same.
A third mapping method is to place the images side by side and then top to bottom. Straight lines are drawn between “landmarks” of both faces, such as the centers of the eyes, the tip of the nose, the corners of the mouth, and the tops and bottoms of the ears. These lines make it easy to see if the eyes, chin, and ears of one photo line up with the same features of the other. If they do not, they cannot be the same face. Analysts use these and other techniques to try to prove that two pictures are not of the same person. With this kind of measurable, scientific proof, the imagery analyst can rule out a suspect.
If an imagery analyst cannot show the images to be different using any method, he will tell police that no differences were found. This is not the same, however, as making a positive identification, which Oxlee says “is only achieved if there is a unique identification mark,” or if the similarities “are sufficiently numerous to be overwhelming.”57 Unless both faces have a scar, mole, birthmark, or other unique feature that can be measured and compared precisely, most analysts can only say that two images show no measurable differences—not that they are, without a doubt, the same person.
Still, photographs and footage are often the most convincing pieces of evidence in a case. “Imagery is the only permanent record of what actually happened during an event,” says Oxlee. “Therefore, it is very important that imagery evidence, where possible, is made available to the court.”58 Court is where a lot of forensic art ultimately ends up, not just photographs and surveillance footage, but composite sketches, facial reconstructions, and age progressions. When art does make its way to court, it has to be strong enough evidence to stand up to a lot of scrutiny by lawyers, judges, and the jury members themselves.