Despite recent advancements in DNA evidence-gathering and high-tech investigative tools, a simple pencil-on-paper sketch can still have a significant impact on criminal cases. Forensic artists who create such sketches use eyewitness accounts, crime scene evidence, skeletal remains, and more to help illustrate and personify criminals and victims—all of it in the pursuit of bringing perpetrators to justice.

To better understand the details of the job, Mental Floss asked three veteran forensic artists about tricks of the trade, why they’re not actually trying to create an exact likeness, and how a bird’s nest can be one of their best tools. Here’s what we’ve learned.

1. Some forensic sketches are inspired by smells.

When witnesses sit down with law enforcement to relay their description of a criminal’s appearance, they might believe the only relevant information is what their eyes have seen. But according to Melissa Cooper, a freelance forensic artist based in California, all of their senses matter. “It often helps to ask questions that will trigger memory recall,” she says. “During one case interview, I asked [a witness] what stood out the most. She said, ‘His cologne.’ You’d think, ‘Oh, great, I can’t draw that,’ but scent is a huge enabler for memory. Now I know she can smell him and she’s right back in the scene. It’s a perfect state to be in.”

2. Forensic artists need to suppress their creativity.

It's easy to imagine that forensic artists might remain hunched over a sketch for hours, trying to insert every last dimple and laugh line they could tease out of a witness. Wrong. According to Cooper, trying to create an exact likeness might make a sketch less likely to resonate with the public. “With a highly realistic portrait, someone might see it who knows the person, but if there’s one thing wrong, one detail, they’ll say, ‘Oh, that’s not my buddy,’” Cooper says. “When it’s more sketchy, more scribbled, you’re leaving more open to interpretation.”

Lisa Bailey, author of Ask a Forensic Artist and a consultant for several law enforcement agencies, agrees. “[Artists] are by necessity keeping their own self-expression and artistry out of it, and not adding information that would create a 'prettier’ image that could lead someone away from recognition.”

3. A skull can tell all.

Courtesy of Lisa Bailey

Forensic artists have responsibilities that go far beyond sketching criminal suspects. Sometimes, they’re called upon to recreate the facial features of a deceased person by “building” out a face using a 3-D replica of a retrieved skull. Teaming with a forensic anthropologist who can usually determine the age, sex, ancestry, and height of the deceased, the artist uses clay to sculpt their missing features. “The skull says so much,” Cooper says. “It can tell you where the eyes angled, where the nostrils went [see image above], where the eyebrows were. Given the choice of a photo of a corpse that’s decomposing or a skull, I’d take the skull.”

4. There aren't a lot of forensic artists working full-time.

By some estimates, there are less than 100 full-time forensic artists in the country. That’s because most of the artists working cases are either freelancers hired by departments or active-duty officers or other agency employees who are called in when needed. “For the average-sized or smaller agency, it doesn't always make sense to have a full-time artist,” Bailey says. “Lots of cases don't require one—there's a video of the suspect, or investigators have already developed leads to the identity of the suspect. Even if an agency estimated the need for 20 or so sketches year, that's still not enough work to justify keeping a full-time artist on the payroll.”

5. Detectives aren't always happy about using sketches.

NYPD via Getty Images

Charles Jackson, one of the "dual duty" artists who retired from law enforcement as a detective in 2013 but continues to provide forensic sketches, says that his fellow investigators were often reluctant to circulate the art he produced. “The most surprising thing about the job is that it’s hard to get detectives to use the tool,” he says. “Generating evidence based on memory, I think they can sometimes be afraid to [have victims] testify to it.” Despite the potential for defense attorneys to call sketches into question, Jackson says that almost all detectives who wind up using them are glad they did. "It's always been a positive."

6. Witnesses sign the forensic sketches.

Once a sketch has been completed and passed on to the investigating officers, it’s considered official police evidence that needs to adhere to a chain of command. To make sure the illustration came from the memory of a specific person, the witness is usually asked to endorse it with a signature. “For a pencil composite, the witness will usually sign the back of the sketch, behind the area of the face so that it won't unintentionally be made public when it's scanned, or can't be accidentally cut off if the sketch is trimmed down to fit in a case file,” Bailey says. The original is then kept on file in an evidence room.

7. Bird nests can be a big help to a forensic artist.

For cases where artists are called to help reconstruct the likeness of a decomposed or otherwise de-featured body, Cooper says that a good reference source for bodies found in the woods can often be found in a very unlikely place. “When dealing with a decomposed body, we’d like to get the color of the hair, and a good place to find that is in a bird’s nest nearby,” she says. “Birds love hair.”

8. forensic artists sometimes give their work as a gift.

Because many forensic artists can be skilled in age progression—trying to realize how a missing child might look years after their disappearance—families with missing loved ones will sometimes inquire about having a sketch done as part of their grieving process. “Sometimes it’s the actual parents, and sometimes it’s just one spouse who wants to give it to the other one,” Cooper says. “I sometimes get scared, not knowing how they’ll react, but they’re usually very grateful.”

9. Forensic artists might be drawing someone police already know about.

Courtesy of Melissa Cooper

According to Jackson, not all sketches are done in the proverbial dark. In some instances, authorities have a suspect in mind and are curious if a witness can match that image with their own description. “Detectives frequently call us to corroborate a suspect they have in mind, so it’s basically a composite sketch for a lead,” Jackson says.

10. Some reconstructions might get a smile.

When Bailey is tasked with sculpting the features of a cold case victim, she pays attention to anything unusual or unique about their teeth. If a tooth is crooked or their smile is distinctive, she may decide to add a little smirk. “If there's anything unusual about the teeth, like gaps or crookedness, then we'll sculpt it with parted lips, or with a small smile, because someone might recognize the person just because of the teeth.”

11. Software helps soften images.

Some departments without the resources to hire forensic artists rely on software that can digitally render faces. While their efficacy compared to hand-drawn images is open to debate, many forensic artists often rely on software when it’s time to prepare a victim's photographed image for public consumption. “There's a lot of work to do to make an image suitable for public release,” Bailey says. “The artist will have to digitally open the eyes, close the mouth and adjust the jaw, remove swathing and cloth that has been placed around the head, and realign the head so the shoulders aren't hunched up around the ears when they are lying on the morgue table.” Bruises, blood, wounds, and other marks are also retouched.

12. Forensic artists can work from surveillance footage.

Not all renderings of suspected criminals come from memory. Sometimes, an artist will be called on to fill in the blanks left by incomplete or obscured surveillance footage. “If they have only a three-quarters shot of someone’s head from above, I can look at that,” Cooper says. “Knowing the anatomy of the head, I can show them what the rest of the person would look like.”

13. Ears can give some forensic artists a little trouble.

Texas Department of Corrections/Newsmakers

Jackson says that many witnesses tend to retain visual information relating to the center of the face: the eyes, nose, mouth, and chin. “People generally have a hard time picking out ears,” he says, mainly because they just didn’t notice them. To assist witnesses with feature identification, some artists use an FBI manual that catalogs many common features and asks interviewees to point out which ones look familiar. Jackson uses one; Cooper doesn’t. “Pictures can be suggestible,” she says. “I like [details] to come from them.”

14. Forensic artists will not draw you a Chupacabra.

Forensic artists occasionally tackle work outside of law enforcement duties: Cooper has worked with the Natural History Museum of Los Angeles with taxidermy efforts for exhibits. But requests to do anything too far off the beaten path are usually met with refusal. “My primary clients are law enforcement, but I once had someone from the Ellen Show wanting me to do a composite of a Chupacabra, which Ellen’s wife apparently saw outside their house,” she says. “Someone else wanted to help interpret a dream for them. There’s an element of integrity to the job. I declined. You get a lot of weird requests.”

15. Luck plays a big part in a forensic artist's job.

Courtesy of Melissa Cooper

Artists working with law enforcement do everything they can to try and take a person’s memories and make them into a tangible image on a page. But no matter how striking the image, nothing will happen unless it ends up in the right place. “We're dealing with luck and timing,” Bailey says. “The right person needs to be looking at the right time. The best, most accurate facial approximation in the world can't do its job if a family member or friend isn't looking.”