In the 1880s, French criminologist Alphonse Bertillon developed a particular obsession with itemizing physical characteristics of prisoners brought in to the Paris police station where he started out as a records clerk [source: National Library of Medicine]. Bertillon painstakingly measured prisoners' arm lengths, head circumferences, ear formations and other anatomical markers; made notes of tattoos and scars; and photographed their facial frontals and profiles. As he amassed this data, Bertillon developed a novel system for identifying inmates, which became known as criminal anthropometry. After French police used Bertillon's identification practices to nab 241 repeat offenders in 1884 alone, this early forensics science spread to other police departments around Europe and the United States [source: National Library of Medicine]. Today, one of the most commonly employed anthropometry tactics that hasn't changed all that much during the intervening century is the police sketch.
The FBI cites an eye witness sketch of Timothy McVeigh as a crucial piece of evidence that eventually brought the mastermind of the Oklahoma City bombing to justice. Ten hours after the 1995 explosion at the Alfred P. Murrah Federal Building that killed 168 people, a forensic artist with the FBI's Investigative and Prosecutive Graphic Unit sketched out the perpetrator's face based on interviews with people who had spotted McVeigh in Junction City, Kan. renting a truck that was later found at the crime scene [source: FBI]. Having seen that relatively rudimentary FBI sketch, Oklahoma State Troopers who later arrested McVeigh on driving- and weapon-related charges unrelated to the bombing didn't release their suspicious-looking prisoner from jail.
Although the McVeigh case is an extraordinary example of a suspect sketch helping successfully nab a criminal on the lam, police sketches are nevertheless a routine part of law enforcement investigations. A forensic artist, who might double as a patrol officer or serve as a civilian contractor, usually interviews crime scene witnesses and victims about a perpetrator's appearance to create a composite sketch. The composite could be drawn completely by hand or computer generated. Sometimes, forensic artists use a combination of the two methods.
But no matter how fine-tuned the police sketch methodology, the most crucial component of an accurate facial composite is an eye witness' memory. Describing the face of someone who might have fled a crime scene or inflicted bodily harm on you might be an erroneous process. The human memory can play tricks, erasing certain details and amplifying others, for instance giving someone a beard when he had a mustache or a square jaw when it was actually rounded [source: Raeburn]. And for that reason, forensic artists must conduct preliminary interviews carefully and with sensitivity to elicit as many precise facial details as possible.
Gathering Clues: Police Sketch Interviews
Before forensic artists can begin composing police sketches, they obviously need an idea of what their subjects look like. For that reason, the eyewitness interview is the most important step in the police sketch process [source: Taister]. Officers or artists doing the questioning need to understand what to ask and how to approach interviewees to cull the most accurate information, since the human memory for faces can be easily fooled. Often, people have a difficult time recalling specific facial features, and the more time that lapses between a crime and the police sketch interview, the fuzzier those memories become [source: Raeburn].
Depending on the crime and the person being interviewed, police sketch sit-downs can last hours. To get an idea of how these question-and-answer sessions are conducted, consider a 2007 study examining people's ability to describe faces for creating forensics facial composites. It broke down the cognitive interview into three phases: rapport building, free recall and cued recall [source: Frowd et al.].
Rapport building simply involves casual conversation -- "Hi, how are you?" -- in an effort to relax the interviewee. Next, the interviewee is asked to recall as many specific details about the criminal as possible. Often, participants begin by discussing hair and general face shape [source: Frowd et al.]. During the last step, cued recall, the forensic artist will ask the interviewee about any defining features they don't immediately remember. At that point, it might be helpful to jog the interviewee's memory with mug shots of previously incarcerated criminals. That way, seeing a similar nose or eyes or jaw line might spark a flashback. Forensic artists may also keep a catalog of celebrity portraits around since the famous faces can spark visual cues as well [source: Raeburn].
While forensic artists keenly focus on minute facial features, former New York Police Department artist Stephen Manusci notes that victims are more apt to provide broader descriptions, such as a "horse face" or "bug eyes" [source: Lichtman]. The role of an adept artist is to break down, or "decode," those vague generalizations into a collection of discrete facial characteristics. That doesn't mean the forensic artist should ever drill someone for more characteristics; pressuring the interviewee might stifle, rather than stimulate his memory [source: Muench]. As the sketch takes shape, interviewees will also begin to either show recognition or point out discrepancies.
Portrait of a Criminal: Composing Police Sketches
Drawing a police sketch by hand clearly requires a degree of artist talent, but it doesn't necessarily demand a degree from art school. Depending on the size of the police department, forensic artists may or may not be full-time employees. In small-town departments, a patrol officer with a knack for drawing may actually volunteer for the role, while larger, better-funded agencies may employ civilians formally trained at the FBI's forensic facial imaging laboratory or other forensic art training programs [source: Echaore-McDavid and McDavid].
The police sketching process also varies by forensic artist. For instance, former NYPD forensic artist Stephen Manusci takes the old school pencil and paper route, refining the face as needed with input from victims or eyewitnesses [source: Lichtman]. Roderick Scratchard, forensic artist with the Philadelphia Police Department, takes the opposite route. First, he creates a computer-generated composite based on photos of faces and features that interviewees have selected. Then, he draws the final police sketch by hand based on that computer composite, tweaking the appearance as requested [source: Avril].
Computers have played a role in police sketches since the 1960s, with the arrival of the identi-Kit composite software. Police departments without the resources to retain a bona fide forensic artist could instead purchase identi-Kit -- and now a host of other programs -- to automatically generate facial composites by selecting from a gallery of profiles and traits. Reliance on computers has proven controversial, however, as studies have shown that hand-drawn police sketches often turn out more accurately than computer-only composites [source: Avril]. Newer programs do a better job at producing more nuanced mug shots. Hearkening back to Bertillon's cross-indexing to pinpoint repeat offenders, a computer program developed at Michigan State University in 2011 digitally analyzes hand-drawn composites and compares them to photographed mug shots stored in law enforcement databases. Due to high recidivism rates, the highly publicized technology could help officers identify suspects more quickly. Nevertheless, the FBI isn't impressed by any technological advances. Due to the anecdotal accuracy, when it comes to the paper versus computer quandary, hand drawn composites are a must-have in the agency's book [source: FBI].
But whether a facial composite is drawn by a person or a computer, the question of whether it looks anything like the person who committed the crime remains sketchy.
Facing Facts: Police Sketch Accuracy and Effectiveness
Forensic artists who have drawn their fair share of facial composites will probably confess an awkward truth about police sketches: They aren't very accurate. By one estimate, hand-drawn composites by trained artists are roughly 9 percent accurate in terms of producing a recognizable likeness to a suspect [source: Avril]. And as we mentioned previously, computer-generated composites statistically tend to be of even poorer quality than hand-drawn sketches, with around 5 percent accuracy [source: Avril].
And it's not necessarily a question of the forensic artists' skill. Even if Leonardo da Vinci were creating police sketches, accuracy issues would still crop up. The major roadblock to creating spitting images of suspects rests not in the forensic artist's hand, but the victim's or witness' memory retrieval processes. If you think about a human face as a chess set, our brains don't capture that image as a collection of knights, pawns and other discrete pieces, which would rely on our recall memory -- memory that requires no priming, such as being shown a picture of someone and asked to identify it. Instead, our brains summon our recognition memory, which relies on cues, such as spotting someone on the street, in order to form the associations that allow us to put, for instance, names with faces. For that reason, we might all know what Brad Pitt looks like and easily identify him strolling down the street, but we'd have a much harder time describing his appearance from scratch.
The violence, stress and trauma of being victim to a crime, as well as the time lapse between the crime and the police sketch interview only muddies recollections [source: Raeburn]. Depending on the circumstances, a criminal's face may never make it through the brain's memory-making process. To store a memory lock-tight, the brain must encode a face, consolidate all of the information about that face (eyes, nose, facial hair, etc.) and catalog it alongside similar-looking faces already stored away upstairs. Cementing that memory for later retrieval during an interview further entails retracing neural pathways by thinking about that face, which might be the last thing a frightened victim wants to do. How easy is it to complete that mental workout in the time it takes to get mugged at gunpoint? Not very.
So why spend time and resources on police sketches if they're neurologically doomed for inaccuracy? Forensic artists argue that the role of police sketches isn't to construct a perfect portrait of the perpetrator. The point of police sketches is to publicize crimes, attract leading clues and get the public looking out for suspicious persons [source: Lichtman]. That's why the artists will highlight standout features -- a tattoo, scar, facial hair -- that might jump out at passersby. After all, happenstance led an Oklahoma State Trooper to pull over Timothy McVeigh less than two hours after the Oklahoma City bombing. But it was that composite sketch distributed by the FBI that eventually tipped off the law enforcement officers that they had a most-wanted criminal on their hands.
How Police Sketches Work: Author’s Note
Though they're quite common, police sketches are one of the most controversial criminology techniques, since they rarely result in a spitting-image representation of a criminal suspect. For that reason, I wanted to get to the bottom of whether police sketches serve any useful law enforcement purpose and whether advanced technology holds any promise for fine-tuning the portraiture process. The U.S. Department of Justice is funding preliminary research into DNA phenotyping, which could potentially offer clues to criminals' appearances based on DNA samples of hair or blood collected from crime scenes. But in the meantime, forensic artists must rely on a combination of strategic interview tactics and portraiture skills to cobble together suspects' physical features. For all of the high-tech forensics techniques showcased today in crime dramas on TV, tracking down a criminal's face remains a surprisingly primitive practice at most law enforcement outposts.
- Adams, Cecil. "How accurate are police sketches of suspected criminals?" The Straight Dope. May 7, 2010. (May 5, 2011) http://www.straightdope.com/columns/read/2937/how-accurate-are-police-sketches-of-suspected-criminals
- Avril, Tom. "How useful are police composite sketches?" Philadelphia Inquirer. April 25, 2011. (May 5, 2011) http://www.philly.com/philly/entertainment/20110425_How_useful_are_police_composite_sketches_.html
- Bruni, Frank. "Doing Police Sketches: ' Not an Exact Science'" The New York Times. June 11, 1996. (May 5, 2011) http://www.nytimes.com/1996/06/11/nyregion/doing-police-sketches-not-an-exact-science.html
- De Grazia, Diane. "The Inventive Genius of Annibale Carracci." National Gallery of Art. (May 5, 2011) http://www.nga.gov/exhibitions/car_degr1.htm
- Echaore-McDavid, Susan and McDavid, Richard A. "Career Opportunities in Forensic Science." Ferguson. New York, New York. 2008. (May 5, 2011) http://books.google.com/books?id=6NADwphGDuwC&pg=PA117&lpg=PA117&dq=forensic+artists+statistics&source=bl&ots=m0XuHWME_e&sig=2i3yWp0CvQH4GV6GnexhtEHIHfg&hl=en&ei=0xTATYO8LMjn0QGU-tCJCA&sa=X&oi=book_result&ct=result&resnum=2&ved=0CCEQ6AEwAQ#v=onepage&q=forensic%20artists%20statistics&f=false
- Enserink, Martin. "Can This DNA Sleuth Help Catch Criminals?" Science. Feb. 18, 2011. (May 5, 2011) http://www.sciencemag.org/content/331/6019/838.short
- Federal Bureau of Investigation. "The 'Art' of Solving Crimes." June 8, 2005. (May 5, 2011) http://www2.fbi.gov/page2/june05/ipgu060805.htm
- Federal Bureau of Investigation. "Forensic Facial Imaging." (May 5, 2011) http://www.fbi.gov/about-us/lab/forensic-science-support/forensic-art
- Frowd, C.D. et al. "An evaluation of US systems for facial composition production." Ergonomics. Vol. 50, No. 12, Dec. 2007.
- Heafner, Horace J. "History of Forensic Art." The Police Artist & Composite Drawings. ForensicArtist.com. (May 5, 2011) http://www.forensicartist.com/history/index.htm
- Lichtman, Flora. "Video Pick of the Week: Composite Sketch." Sept. 24, 2010. (May 5, 2011) http://www.sciencefriday.com/program/archives/201009246
- Michigan State Police Department. "Forensic Art 101." (May 5, 2011) http://www.michigan.gov/msp/0,1607,7-123-1589_3493_22454-59999--,00.html
- Muench, Sarah. "Police sketches aided 'Chandler Rapist' investigation." The Arizona Republic. Feb. 1, 2008. (May 5, 2011) http://www.azcentral.com/news/articles/0201sketch0201.html
- National Institute of Medicine. "Alphonse Bertillon (1853 - 1914)." Updated June 15, 2006. (May 5, 2011) http://www.nlm.nih.gov/visibleproofs/galleries/biographies/bertillon.html
- Raeburn, Paul. "Forensic Artists Use Talent to Solve Crimes." Science Friday. NPR. Sept. 24, 2010. (May 5, 2011) http://www.npr.org/templates/story/story.php?storyId=130104055
- Saletan, William. "Race, Genes, and Criminal Justice." Slate. March 30, 2009. (May 5, 2011) http://www.slate.com/blogs/blogs/humannature/archive/2009/03/30/race-genes-and-criminal-justice.aspx
- Taister, Michael A. "Forensic Art and Illustration." January 2001. (May 5, 2011) http://www.fbi.gov/about-us/lab/forensic-science-communications/fsc/jan2001/taister.htm
Police Sketches: Cheat Sheet
Stuff You Need to Know:
- In the 1880s, French criminologist Alphonse Bertillon painstakingly recorded the physical characteristics of Parisian prisoners, an early practice that would evolve into police sketches.
- The FBI cites an eyewitness sketch of Timothy McVeigh as a crucial piece of evidence that eventually brought the mastermind of the 1995 Oklahoma City bombing to justice.
- An eyewitness interview is the most important step in the police sketch process. Forensic artists who create police sketches may also jog interviewees' memories by showing them mug shots of previously incarcerated criminals or celebrities with similar facial features.
- Police sketches don't have a great track record for accuracy. According to one estimate, hand-drawn composites by trained artists are roughly 9 percent accurate in terms of producing a recognizable likeness to a suspect.
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