Over the last decade or so, there has been a notable rise in public interest of criminal investigations. Due in part to the growing popularity of police dramas on television and the creation cable channels such as Investigation Discovery, which focuses on violent crime investigation, people are now more aware then ever of the processes involved in police work. Unfortunately, many misconceptions arise out of the need to sensationalize television. Terms like “psychological criminal profiling,” “MO,” and “signature analysis” often get thrown around inaccurately, leaving the general public, and often police officers themselves, with the wrong impression of what these terms mean in relation to a criminal investigation. Modus operandi (MO), Latin for “method of operation,” is the manner in which a crime is carried out. It is the description of all of the behaviors and actions that are necessary for a particular offender to successfully commit his or her crime (Turvey, 2012, p.334). As such, it is also all of things that someone does during the commission of their crime to ensure that they will not be identified or caught. In sum, according to Turvey, a person’s MO serves three general purposes: protection of offender identity, successful completion of the crime, and facilitation of offender escape (p. 336). It doesn’t tell criminal investigators about someone’s motivations, but rather simply about their actions. In this way it is the concrete evidence at a crime scene.
When attempting to link several similar cases together, MO has great significance to investigators. Identifying the similarities among methods of operation is a critical step in crime scene analysis that provides the “resulting correlation that connects cases” (Douglas & Munn, 1992, p. 3). An offender’s MO can be simple or highly complex depending on the degree of sophistication indicating the experience, motivation, and mental aptitude of the offender. Law enforcement analyzes the criminal behavior of an offender through his or her MO (Hazelwood & Warren, 2003, p.588). Because it can be an indicator of a criminal’s level of sophistication, the method of operation can change over time, and even vary from crime to crime depending on circumstance. A burglar may learn better ways to pick locks, may become savvier about what items have the most value, and may gain confidence committing his crime, perhaps causing him to be more thorough and spend more time at the crime scene. In the case of a sexual assault, one perpetrator for example, an 18-year-old rapist, did not use a condom during a rape and was subsequently convicted based on DNA evidence recovered from the victim. He was released after serving a seven-year sentence. He was back to his old ways within a matter of months. However, this time he wore a condom (Hazelwood & Warren, p.588). Offender MOs are dynamic and subject to change throughout the course of an offender’s criminal career. The danger of getting caught may become more or less present, causing an evolution of methodology and technique in order to evade capture. This is a result of gaining experience and knowledge, natural maturation, and perhaps education. If a perpetrator gets caught, he will learn from the mistakes he made and refine his methods so as not to have the same actions give him away a second time, such as in the case of the rapist described previously (Douglas & Munn, p. 2). Many offenders who serve time in prison also learn a lot of valuable information about how to improve their criminal conduct from their fellow prisoners. Offenders may emerge from prison as a wiser, more dangerous criminal due to the refinement of their MO during the course of their incarceration. Each stint in prison many create more sophisticated violent serial offenders. Victim response and availability plays a part in refining an offender’s MO, as well. A sexual predator may initially have trouble controlling or subduing his victims, so he may modify his methods to minimize the struggle. Pre-planning may become more involved with greater thought going into the types of weapons or ligatures he may use on the victim. Another situation which may change a perpetrator’s MO is an escalation of violence. A rapist may not initially set out to kill, but through the course of the crime, he may accidentally or purposely kill his victim to protect himself from harm or being caught. Offenders continually redesign their MO to adapt to the conditions of the crime (Douglas & Munn, p. 2). While an offender’s MO is subject to change and evolution, it does not mean that all aspects of how they operate will change. Certain actions may have served them very well in the past. Having successfully committed a crime and gotten away with it, a violent serial offender will continue to use those same actions in future crimes. Behaviors will become familiar and comfortable to a criminal; therefore they will become better at anticipating the outcomes of them (Hazelwood & Warren, p. 589).
Modus operandi is significant to a criminal profiler’s work because it provides several key pieces of information about an offender. In addition to the choices, procedures, and techniques used by violent criminal offenders, MO can also point toward a person’s particular skills or profession, both in a criminal and in a non-criminal sense. Details that indicate a deeper level of foreknowledge can also reveal if the perpetrator conducted prior surveillance of the victim or crime scene before the crime was carried out (Turvey, 2012, p. 335). Despite the obvious value in identifying an MO, criminal profilers and investigators must always be careful not to place too much weight solely on a criminal’s MO because, as previously mentioned, there is significant opportunity for an offender’s methods to change over time. Much more specific to an individual violent offender is the signature that they leave at the crime scene.
Criminal signature is the actions that have nothing to do with carrying out the crime or getting away with it. Signatures are important to the offender in a personal way. Torture, humiliation, repeated stabbing, postmortem mutilation, and the takings of souvenirs are some examples of criminal signatures. These actions are often described as the “calling card” of an offender and cover the unique combination of behaviors that emerge across two or more offenses (Hazelwood & Warren, 2003, p. 591). These actions are unique to each perpetrator and provide psychological insight into the person’s underlying motivational behavior for committing their crime. The signature aspects go beyond what is necessary to commit a violent criminal act, playing into the fantasies of the offender. Turvey (2012) describes four marks of a true criminal signature: it takes extra time to carry out then just the completion of the crime, it is unnecessary for the completion of the crime, it involves an conveyance of emotion, and it may involve the expression of fantasy (p. 344). The drive to commit violent acts is not enough to satisfy the psychological needs of the perpetrator, so they must go one step further and perform some sort of ritual with their victim and/or crime scene. The crime scene is the stage on which the violent rapist or serial killer acts out his psychological and physical fantasies. An example of signature behavior a rapist may display are acts of domination, manipulation, or control during the assault of his victim and using exceptionally vulgar or abusive language, or preparing a script for the victim to repeat. The use of excessive physical forces and the order of activities a rapist may engage in with all of his victims is also an example of signature behavior (Douglas & Munn, 1992, p.3). While a criminal’s signature may evolve over time, it will never change. Violence and degree of mutilation or degradation of the victim may escalate with each progressive crime, but the essential elements of the perpetrator’s ritual will stay consistent, as his psychological motivation for committing crimes remains unchanged. Signatures may not show up in every crime scene. Offenders may get interrupted, or decomposition of a homicide victim can erase the traces of the ritual performed during the crime. When the signature is present, though, it can provide the most valuable clues to linking several similar cases to one offender.
A specific example of the importance of an offender’s signature is the case of Nathaniel Code, Jr., who was convicted of murder in Louisiana for crimes he committed between 1984 and 1987. His MO was very different in all of his crimes, so at first it may have seemed like the crime were not committed by a single offender. In the first crime, the offender gagged his victim with a piece of material obtained at the crime scene, but brought duct tape to use on the seven other victims in the incidents. In addition, Code stabbed and slashed the first victim, whereas the victims of the other crimes were also shot and strangled. The victims ranged in age from 8 years to 74 years and included both sexes; however, all were black. He also offender took money from one crime scene, but not the other two. In this case, MO would have failed to link the crimes together. But Nathaniel Code, Jr. left his "calling card" or signature at every crime scene – the binding and killing of each victim - and thus investigators were able to link Code to all of the offenses (Douglas, & Munn, 1992, pp.2-3). This evidence was enough to convince a jury that he was the sole perpetrator at each crime scene. Testimony regarding the signature of a series of crimes is often presented in the courtroom to connect multiple crimes to the same offender (Hazelwood & Warren, 2003, p. 592). This is one of the key legal differences between MO and signature, as a criminal’s MO alone is not admissible as evidence in court.
A particular criminal’s MO is comprised of the choices and actions that help them commit their crime. It is a reflection of how the crime was committed. In contrast, a criminal’s signature indicates the offender’s motives and indicates why the person committed the crime (Turvey,2012, p. 334).The two criminal indicators are very useful when used in combination during an investigation to profile a suspect, but MOs are not usually as unique and individual as a signature. An offender’s method of operation can be thought of to be class characteristics of physical evidence at a crime scene, while the signature can be thought of to be an individual characteristic. For example, in the case of a series of rapes, MO narrows down the pool of possible suspects to sexual offenders, eliminating robbers, car thieves, and drug dealers. Signatures aspects, when present, home in a specific psyche of one individual who has expressed his individual needs and desires, his fantasies. The recurring patterns that conform to the particular style of a serial sexual offender found at multiple crime scenes point to the crucial role of fantasy in these crimes. The MO of serial crimes may adapt and change as the perpetrator becomes more experienced, but the fantasy that drives these behaviors is static and unchanging from crime to crime. It is this fantasy that represents the serial offender’s signature. Psychologically speaking, it serves the function to replay childhood trauma into a scenario where the perpetrator has control over the situation in order to bring conquer to their mental distress (Kocsis, 2006, p. 78). The subtle elements of a signature behavior may change over time, but the underlying core features will never change.
One of the most well-know and studied cases of serial murders is that of Jack the Ripper. Between 1888 and 1891, 11 female victims were murdered in the Whitechapel area of London, England. One of reasons for the fascination with his crimes is that no suspect was ever been tried or convicted. Although there is much debate about which and how many of the murders can be linked to one individual, many experts agree that at least five of the victims can definitively be tied to one killer. Because of the interest in the Whitechaple murders, there is a great deal of evidence and information available about Jack the Ripper’s crimes and it provides an excellent case study on MO versus signature. The MO of the Whitechaple killer changed from one murder to the next as the perpetrator learned more effective techniques. The actions that went above and beyond what were necessary to kill the victims were the unique criminal signature of Jack the Ripper. It is the combination of those signature behaviors that several of the victims can be linked to one offender (Keppel, Weis, Brown, & Welch, 2005, pp. 19-20).
Since a serial offender’s modus operandi can and often does change, it is not the most useful method of linking cases together. Looking instead at the criminal’s repeated ritualistic behaviors at the crime scene is often more important in connecting several crimes to the same person than considering only his criminal techniques (Schlesinger, 2009, p. 82). More consideration should be given to a crime scene’s signature aspect than victim similarities, as well, although victim characteristics should never be discounted completely when attempting to link cases to a single serial criminal. A perpetrator of violent serial crime expresses emotions and anger through rituals, not by attacking a particular type of victim who possesses specific characteristics or traits (Douglas & Munn, 1992, p. 5). Douglas and Munn provide an example of the differences between modus operandi and signature in the cases of two bank robberies. A robber in Michigan made the bank tellers undress during the robbery. Another bank robber in Texas also forced tellers to undress, but he also made them pose in sexually provocative positions while he took pictures. The robber in the Michigan case used an efficient technique to offer him more time to escape - the tellers needed to dress before they called the police. The tellers offered vague descriptions of the perpetrator because their embarrassment prevented them from making eye contact with the robber. The Michigan robber used a smart MO. However, in the Texas case, the robber went a step beyond the necessary steps to effectively commit his crime. He made the tellers act out his fantasy by posing for photographs; that was his signature. The bank robbery along did not satisfy his psychological sexual needs (p. 5). Using MO and signature behavior to connect several cases to the same perpetrator is called case linkage. Case linkage is a critical part of the investigative process. Criminal profilers engage in both inductive and deductive criminal analysis to compile the most accurate picture of the perpetrator of violent crimes.
One goal of criminal profiling is to “provide the criminal justice system with a social and psychological assessment of the offender” (Holmes & Holmes, 2009, p. 9). This initial goal narrows the scope of the investigation by identifying basic traits of the perpetrator such as race, age, education, etc. This will provide law enforcement with a profile of the suspect they should be looking for. The second goal is to give investigators a “psychological evaluation of belongings found in the possession of the offender” (Holmes & Holmes, p. 10). What this can provide is a list of particular items that law enforcement officials should look for when they have found the person who they believe is the perpetrator of the crime. Souvenirs, photos, and fetish items can serve to confirm that the personality or behavior type of the suspect matches that of the proposed profile. The third and final goal of criminal profiling provided by Holmes and Holmes is to “provide interview suggestions and strategies” (p. 11). To conduct a successful criminal profile, one must look at all of the information available regarding the crime scene, the victim, the forensic evidence, and the details of the commission of the crime. This where case linkage is most valuable and the use of MO and signature aspects come into play. An inductive criminal assessment compares the similarities that exist between crimes to make the basic assumption that people who commit certain crimes in certain ways share characteristics with criminal who have committed similar crimes in similar ways. This is an example of an offender’s MO. As previously mentioned, an individual gains more experience and confidence with his crimes so his techniques will change to increase his efficiency and therefore an individual’s MO often changes over time (Schlesinger, 2009, p. 78). Because of this, using a criminal’s MO is not useful on its own to linking a series of crimes to the same offender. In this way, the inductive criminal assessment may not be adequate to follow the work of a single offender over the course of their crimes. Alternately, a deductive criminal investigative assessment will take into account a variety of factors that lie behind an offender’s motivation to commit a crime. This is marked by his signature, that unique manner in which he commits his crimes (Holmes & Holmes, p. 48). A deductive criminal assessment will factor in the physical and emotional characteristics of the crime to develop a more accurate offender profile of a single killer. In one example of an early case of a deductive analysis, was the case of the “Mad Bomber” who struck New York City in the mid 1950s and went undetected for almost 16 years. The New York Police Department finally sought out the services of psychiatrist James Brussel to examine all of the evidence including letters the offender had sent to the police, crime scene photographs, and descriptions of the home-made bombs. Brussel concluded that the individual they were looking for was “… a heavy man. Middle age. Foreign born. Roman Catholic. Single. Lives with a brother or sister. When you find him, chances are he’ll be wearing a double-breasted suit. Buttoned.” (Schlesinger, pp. 74-75). His assessment led to the capture of George Metesky, who fit Brussel’s profile down to last detail of the buttoned suit. Brussel had used a series of deductive reasoning to develop his profile. Instead of evaluating the mental health of a given person, he simply worked backwards from the information he was given (Schlesinger, pp. 74-75) Here, instead of looking at just the methods with which Metesky carried out the bombings, Brussel delved deeper into the signature aspects of the crimes that allowed for an evaluation of the psychological motivational factors behind the crimes. This type of deductive criminal analysis work is typically done by mental health professionals who are better trained to make assumptions about possible offenders based on their behaviors and motivations. On the other hand, inductive criminal assessments are often done by police investigators who examine the actions carried out during a crime to compare them to other known criminal acts.
While both MO and signature offer valuable insight to the personality of a criminal, the signature is a much more unique personal identifier. A well-trained criminal profiler will consider both the methods used to carry out the crime and underlying motivations that show up in the perpetrator’s signature behaviors. By using both inductive and deductive criminal assessment techniques, crime investigators can bring all of the pieces of the crime scene puzzle to achieve a successful criminal personality profile and hopefully provide an accurate suspect for serial crimes.
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