Modus Operandi

The modus operandi, often referred to as MO, are specific actions taken by a perpetrator in order to complete a crime. To be considered part of an MO, an action must be necessary and not superfluous to carrying out the crime. As a whole, the MO is a set of learned behaviors that are used because they work. An example of an MO for a rapist might be to hang out in shopping mall parking lots at night, force an unaccompanied woman into her car at gunpoint, and rape her. The MO may evolve over time as the criminal gets better and more efficient or suffers setbacks because of a particular method. The evolution of an MO is textbook operant conditioning, a form of learning. It describes a set of voluntarily learned behaviors that are modified as a result of the consequences created by the behaviors in the environment. Thus, as most criminals attempt to improve, we can expect to see their MO change gradually over time. All Dexter fans can describe their hero’s MO. But let’s learn more by taking a look back and identifying Dexter’s original MO, its evolution, and, finally, his current strategies.

We saw Dexter’s first kill in “Popping Cherry” (1-3). The victim, Mary, a.k.a., The Angel of Death, was a murderous nurse attending to Dexter’s foster father, Harry, in the hospital. Harry encouraged Dexter to commit the murder and Dexter did so in the victim’s own apartment home, while her cat looked on apathetically. Of his first kill, Dexter stated, “Things were a little messy in the beginning. Hey, perfecting a new craft takes time.” We saw that the entire room was covered in plastic, as was Dexter himself. Wearing what appeared to be a plastic hoodie and pants, Dexter waited for the nurse. When she arrived home, Mary walked into the prepared kill room calling for her cat. She was clearly bewildered by all the plastic, but alert; Mary spotted Dexter well in advance as he lunged toward her with a syringe of M-99, and foiled his initial attack. A physical struggle ensued. The two wrestled until Dexter got the upper hand and pinned Mary to the ground. She was finally subdued by a punch to the face. Unconscious for a time, she eventually awoke and found herself gagged and naked in the plastic-wrapped kill room, bound to a table. Fearful, she looked around. Dexter was sitting on the couch leafing through a scrapbook that contained mementos of her victims. Spotting him, she let out a muffled yell. Dexter leapt from the couch and grabbed a knife. Walking toward his helpless victim, he ordered her at knifepoint not to scream, stating that if she did, she would “lose a tongue.” Having gained compliance, Dexter removed the gag and allowed Mary a brief explanation for her crimes. Hearing it, he re-inserted the gag and began to stab her repeatedly in the side.

As compared to his slip-ups with Mary, Dexter’s future murders were more sophisticated. Re-watching the very first episode, “Dexter” (1-1), it is clear that he had come a long way since that first kill. Dexter’s victim, Mike Donovan, was a forty-something boys’ choir director who had murdered at least three children. On the night of the kill, Dexter stalked his victim at an outdoor concert. He lay in wait, unseen in the dark night, for the choir director in the backseat of his vehicle. The concert ended and Mike walked down the road to his car. He settled into the driver’s seat, plainly oblivious to the danger that was awaiting his return. Dexter swiftly and expertly popped up and choked him into submission with wire. Dexter directed the bound and gagging but still conscious victim to drive to a remote cabin in the woods. As the car came to a stop, three empty graves were visible in the light of the headlamps. Enraged, Dexter violently dragged Mike from the car and into the cabin where the remains of three young boys were displayed on plastic wrap. He forced the terrified man to look at the decaying bodies and admonished him for what he had done to the boys. Standing against the cabin wall crying, Mike admitted, “I couldn’t help myself.” Dexter, facing him, listened and responded to his pleas and justifications, then stepped forward and abruptly sedated him via injection. Conscious again, Mike found himself gagged, nude, and tied to a table with plastic wrap. Dexter was clad in what we would later learn was his traditional kill suit, an apron, and a welding mask. Seeing that Mike was awake, he quickly went to task. Grabbing a scalpel, he moved to his victim and made a small incision on right side of his face. He took a blood sample from the bleeding wound, encasing a droplet of blood between glass slides. This completed, Dexter chose a tool—a saw—and killed the man by sawing his neck. In the process Dexter stated, “Soon, you’ll be packed into a few neatly wrapped Heftys and my own small corner of the world will be a neater, happier place.” The show cut immediately to Dexter in his boat, and viewers were left to presume that Dexter chopped up Mike’s body, loaded it into garbage bags, and dumped it in the ocean.

By comparing the case of Mike to that of Mary, we can see that Dexter had made a few noteworthy changes to his MO to lessen the risk of being caught. First, he learned that it was easier to subdue his victim from behind. Caught from behind, the choir director was unable to see the attack coming, unlike nurse Mary, who did and had opportunity to prepare and fight back. Second, Dexter learned that it was safer to make the initial attack in a less-populated location. Although Mike was apprehended after a well-attended concert, his car was parked on the side of a dark road. This was in contrast to Mary, who was assaulted in what appeared to be an apartment building, most likely populated with close-by neighbors. This led to the third change, a more remote kill room. As compared to Mary’s apartment, Dexter dramatically decreased his chances of getting caught at Mike’s remote cabin. Fourth, Dexter had perfected a quick kill. Mike was presumably killed and therefore silenced after the first cut to his neck, while Mary yelled, albeit muffled by the gag, with each stab to her side. Finally, we know that Dexter had mastered the prep required for both himself and the kill room. With the more sophisticated kill suit and kill room in Mike’s case, it was likely that Dexter dramatically reduced his prep time and risk from that in Mary’s.

Considering the facts of the two cases, we can ascertain that generally, Dexter’s MO has evolved with experience. Learning from each kill, he added improved techniques, thereby working toward perfecting his craft. This is consistent with research on serial offenders, which suggests that learning occurs from challenges faced during the commission of crimes, as well as slip-ups that lead to arrests. In this way their MOs, like Dexter’s, are dynamic. As the show enters its fifth season, Dexter fans know their conscientious and morally minded serial killer’s current MO. Barring unusual circumstance, Dexter researches his victims and then completes a stakeout of their typical haunts. He learns their behavioral patterns and then plans the kill, finding an appropriate kill room. The victims are stalked and subdued, usually with M-99 or wire, and brought unconscious to the pre-prepared and plastic-covered kill room, where they are secured to a table and killed. Did I leave out some details? The nudity, the cut on the cheek, the blood slide, the little talk Dexter has with each victim? No. These are not part of Dexter’s MO. This is because they go beyond the acts necessary for him to carry out the murders. They are much too personal. As such, they can be considered part of his “signature.”

The Signature

The signature, sometimes referred to as a “calling card,” is another element of criminal behavior that occurs during the commission of a crime and entails all the aspects of criminal behavior that go beyond those necessary for the completion of a crime (the MO). A signature is most likely to be used by serial offenders like Dexter and is more unique to them than their MO. A comprehensive analysis of a serial killer’s signature may reveal his psychological traits, needs, and deviancy. This is because it involves the parts of the crime that are not necessary for its completion and may in fact point toward the personality and unique desires of the perpetrator. In Signature Killers, Dr. Keppel states further that the signature is something that the serial killer is “psychologically compelled to leave to satisfy himself sexually.” Surviving victims and crime scenes can provide behavioral information that lead to clues about an offender’s signature. Examples may include exceptionally detailed, abusive, or vulgar language, excessive use of force, scripted conversations or behavioral patterns, and actions taken to produce certain psychological trauma such as domination or humiliation.

Dexter has a clear signature. Viewers may see the clues that point to his identity in the signature left during the commission of many of his crimes, but Miami Metro has yet to be tipped off. In the great majority of Dexter’s murders, the trained killer and police employee does not leave a crime scene or a body behind. Like his MO, Dexter’s signature is still safe with his viewers. Let’s take a look at it now and all that it reveals about his fantasies, or, in other words, Dexter’s deep psychological needs.

To begin, we must revisit Dexter’s crimes and take note of each behavior completed in excess of that needed to kill the victim. Dexter’s signature involves all of the elements of the crime not identified above, using the cases of Mary and Mike, as part of his MO. These elements include a conversational component, psychological trauma to the victim, a particular, almost scripted time sequence or order of events, and excessive use of force postmortem.

Perhaps one of the most noteworthy aspects of our hero’s signature is the fact that he engages each of his victims in some type of conversation about their own victims. These conversations tend to occur at a particular time in the sequence of events leading up to the kill (i.e., once the victim awakens secured to the table) and are prompted by the setup of each kill room. In the case of Mary, Dexter was able to prompt a conversation when he located a scrapbook the nurse kept with information about each of her victims. When she awoke, Dexter stated, “I’ve just been looking through your photo album . . . hope you don’t mind. (Showing her the album) Are all your victims in here?” (“Popping Cherry”). He walked over to her and removed the gag for her to respond. “I helped them, all of them. I took their pain away,” she pleaded in her defense. “I understand,” said Dexter calmly, adding, “Now it’s time to take away your pain,” and commenced to stab her in the side. Years later, Dexter prompted a similar conversation with victim Mike by forcing him to look at the decaying bodies of his three young victims. In this case, Dexter uncharacteristically prompted the conversation earlier in the sequence of events—prior to the injection and securing the victim to the kill table. The effect, nevertheless, was the same. Seeing the bodies, the choir director begged for his life, and Dexter directed the conversation toward Mike’s victims, asking if they also begged.

“I couldn’t help myself,” cried Mike in his defense. “I couldn’t, I . . . please, you have to understand.”

With initial understanding, Dexter replied, “Trust me, I definitely understand. See, I can’t help myself either.” Then, his tone swinging toward anger, said, “But children, I could never do that, not like you. Never, ever kids.”

Interested, Mike whispered, “Why?”

“I have standards,” replied Dexter as he stepped forward to inject the child killer with M-99.

Neither this conversation, nor that with Mary, was necessary for the completion of their murderers. As such, it follows that a conversational component is one piece of Dexter’s signature. So what might a thorough analysis of his pre-murder conversations reveal about our serial killer’s psychological traits, needs, and deviancy? First, it seems safe to conclude that Dexter derives some sort of personal satisfaction from hearing the victims admit to their own crimes. This might fulfill a need for vigilante justice or righteousness. Alternatively, the conversation may simply fulfill Dexter’s need to adhere to Harry’s Code: hearing the victim’s admission of guilt assures that Dexter has a viable victim on his kill table. The conversations also tend to cause the victims some sort of psychological distress, often leading to tears, justification, and/or begging for their own lives. They may be meant to invoke fear, guilt, or remorse. In any case, the nature and setup of the conversations seem to point toward such psychological traits as grandiosity and desire to dominate. This is in stark contrast to Dexter’s usual presentation in his daily life as a considerate, agreeable people pleaser. So which version of Dexter is the real Dexter? Criminal investigators may say the former. Experts believe that the signature aspects are repressed fantasies that the serial killer holds on to and daydreams about until he is compelled to act. Viewers may say the latter. Privy to Dexter’s internal monologue, we know that there is more to Dexter than his Dark Passenger.

Another element of Dexter’s signature is that the victims are stripped nude prior to their murder. Oftentimes they are also nude during the conversation. The nudity, like the conversational component, suggests the intentional infliction of psychological trauma on the victims. Psychologically speaking, the nudity points toward traits of aggression and domination. It may also signify Dexter’s need to shame or humiliate his victims.

A third integral signature piece is the small cut Dexter makes on most of his victims’ cheeks. When this occurs, either during or following the conversations, Dexter also takes a sample of their blood and places it between two glass specimen slides. He takes the slide home and stores it in a trophy-like box filled with his other victims’ blood samples. Like the conversation and the nudity, this particular behavioral pattern also stands out as clearly unnecessary to the act of murder. Moreover, it evolved over time. Dexter did not take a blood slide from Mary, his first kill, but he did with Mike, and we continue to see him taking them from a majority of his victims.

This element is ripe for analysis. The taking of a blood slide psychologically reaffirms the trait of domination or control, as well as order. There is a certain sense of power and forced intimacy Dexter supposes in the performance of such an unusual action without explanation or obvious reason provided to the victim. Viewers can assume that cut provides Dexter with an opportunity to act out his childhood experience as a witness to his mother’s murder, this time in control as the aggressor. As we saw in “Born Free” (1-12), at some point during the crime young Dexter had endured a cut to his left cheek. Moreover, there is clearly some need to memorialize the murders and retain physical access to the memory in the future—like a prize. They help Dexter to relive the thrill of his kills. Finally, the slide aspect suggests a deviancy, a sort of abnormal gratification from blood or the orderly placement of blood. Dexter’s career as a blood spatter analyst supports this conclusion.

There are times, however, when Dexter does not seem to experience these needs, which explains the instances when no blood slides are taken during the kill. This is most apparent in unplanned or personally meaningful or unmeaningful kills. In regard to unplanned kills, such as Esteban and Chico, the drug dealers who arrived at the cabin where Sergeant Doakes was held captive in “Left Turn Ahead” (2-11), Dexter killed out of practical necessity or impulse. The brooding fantasy or psychological need to kill was not present. As such, Dexter had no desire to memorialize the event. The same explanation can be applied to Dexter’s meaningful kills. He did not take slides, for instance, from his brother the Ice Truck Killer, Lila his one-time girlfriend and Narcotics Anonymous sponsor, or Camilla Fig, family friend and retired police department employee. All of these individuals were personal to Dexter and he had no desire to recollect the kills. In the same vein, Dexter does not take slides for unmeaningful kills. For example, with Ken Olson in “Dex, Lies, and Videotape” (2-6), Dexter said, “No, I’m gonna kill you. I have to, I just don’t need to . . . It’s very empowering.” This statement and Dexter’s failure to take a blood slide suggest a lack of fantasy prior to the kill, and once again, no need to memorialize it.

The final piece of Dexter’s signature is the excessive use of force postmortem. Dexter’s current MO tends to involve a quick killing blow to the victim, usually a fatal stab wound to the chest, neck, or head. Any postmortem mutilation following the fatal blow is in excess of that necessary to accomplish the murder and by definition becomes part of Dexter’s signature. Following the fatal blow, Dexter saws or cuts up the body into smaller pieces. This is referred to by forensic experts as “overkill.” It produces a great deal of mess and blood that he easily cleans up using the plastic and garbage bags. Dexter’s excessive use of force suggests psychological traits toward extreme violence, aggression, and anger. This behavior could also function as self-protection, maybe a clean and efficient way to follow Harry’s Code and dispose of the body. But disposing of the body in one piece would arguably produce the same effect more quickly. Dexter does, after all, dispose of the body parts in the same location and leaves identifying marks, i.e., teeth and fingerprints, intact. This overkill suggests a need to not only kill his victims, who are murderers of innocent people, but literally slaughter them, defiling their bodies and rendering them unrecognizable. Like the blood slides, the process of this act may point toward a deviant gratification from blood.

Experts believe that an analysis of the signature elements, like those just described, can also reveal the criminal’s fantasies. This is important because fantasies are thought to be the driving force behind the crimes committed by serial offenders. If the fantasy is that of humiliation, for example, the criminal may pose his victims in degrading ways before or after he tortures, kills, or rapes them. When he offends again, the fantasy will be repeated and the degrading poses will be his signature. The signature aspects may evolve or become more complex over time, but their underlying theme remains the same.

In regard to Dexter, we can piece together each of his signature aspects to deduce the fantasies that drive him to murder. From them we might conclude that Dexter has fantasies of dominating, shaming, manipulating, and controlling murderers of innocent people. Furthermore, he probably fantasizes about replicating the fear within them that their own victims felt. Finally, Dexter has fantasies of being both an aggressor and avenger of the innocent. This is evident in “The Dark Defender” (2-5), where Dexter dreams about saving his mother from her killers while dressed as the superhero. These fantasies are consistent with those typical to survivors of childhood abuse who sometimes have fantasies of being in control in the role of the aggressor as adults. As a young boy, Dexter witnessed the brutal murder of his mother and sat in her blood with her sawed-up corpse for several days before being rescued by Harry. It is not unimaginable that he would have both a strong unconscious drive toward aggression as well as conscious fantasies, or daydreams, now as a young and capable man psychologically tormented and angry about his mother’s murder.

Although Dexter plays out these fantasies in most of his murders, he does not, or sometimes is not able to, conduct all of the signature aspects in his crime. This is consistent with real-life serial killers as well. Crime scene investigators believe that serial criminals do not always leave signature aspects at all crime scenes. From time to time the criminal will not be able to complete the signature aspects of his crime. Factors such as time, victim behavior, or unforeseen events like intrusions can prevent him from completing the behaviors beyond those necessary to commit the crime. When this occurs, he is often less satisfied with the crime because he was unable to act on his fantasies.

In the case of Dexter, all of these factors are relevant. Time or unforeseen interruptions have occasionally precluded the completion of signature aspects, as in the murders of Valerie Castillo, Nathan Marten, and George King. With Valerie Castillo, wife and accomplice to Jorge Castillo in a coyote operation involving Cuban immigrants, Dexter ran out of time and was unable to perform his ritual overkill. With Nathan Marten, photographer and sex offender, the kill by strangulation was an impulsive reaction to catching Marten viewing photos of Rita’s children. With this victim, the lack of pre-planning and time seemed to preclude the completion of signature aspects and Dexter did not seem as relieved by the kill. Lack of preparation, time, and anxiety all precluded Dexter’s completion of signature aspects and satisfaction with the killing of George King, a.k.a, the Skinner. With this kill the tables were turned, at least initially. Dexter was caught by the Skinner and nearly became his victim, only to overpower the man at the last moment, breaking his neck and tossing him into the path of an oncoming police car just in time to escape from the scene unnoticed. In addition, some kills, like those of his brother, Brian Moser, a.k.a., the Ice Truck Killer, or Camilla Fig, do not seem to justify the signature aspects, since they are meaningful and personal. Dexter does not enjoy or get the same satisfaction from them and so would not get any gratification from his usual ritual.

Victimology

A third element of crime scene investigation is victimology, or simply the characteristics of the perpetrator’s victim. Victimology may include the victims’ age, gender, race, occupation, physical attractiveness, relationship status, or perceived vulnerability, to name a few. Sometimes there is an identifiable likeness in victims chosen by serial offenders because they prefer a certain type of victim, while other times there is not. For instance, some criminal behaviors are motivated by an emotion experienced by the perpetrator, such as rage or anger, and the victim may be chosen on the basis of availability. Dexter fans know that his victims do tend to have one personal trait in common: a history of killing innocent people. Only a few of the many do not share this history, including Camilla Fig and Nathan Marten, and in those cases Dexter’s traditional MO and signature were noticeably absent.

If we were to examine only the cases of Mary and Mike, we might see more to the victimology than what is really there. Both of those victims were white and middle-aged. However, if we take a look at Dexter’s other victims, we can immediately discount both characteristics. In regard to race, we need to look no further than the first season’s Jorge Castillo and Alex Timmons, a sniper, who were, respectively, Hispanic and African American. Turning to age, we see that both of these victims were considerably younger than Mary and Mike, but if we still are not convinced we can look to Freebo, a drug dealer and murderer of two college girls in season three, who was likely in his twenties when Dexter killed him. It is easy to see how, without the benefit of insider knowledge, just studying the traits of a few similar victims could lead to inaccurate beliefs about victimology.

Still, victimology has its uses. In many cases, understanding a serial killer’s victimology can lead to a greater understanding of his psychology. In season four, the Trinity Killer was so named because he was originally believed to kill in patterns of three—first a young woman, followed by a mother, and then a man. This basic victimology was first uncovered by Lundy and, paired with the MO, allowed the investigator to link many murders over a number of decades to Trinity. In Miami and too close to his man, Lundy was killed by Trinity’s daughter Christine, but Dexter persisted where the investigator left off. He soon uncovered a fourth victim in Trinity’s pattern—a young boy. We then learned that Trinity’s victims’ characteristics bore a shocking similarity to the psychological traumas he had experienced as a child. In fact, the young boy that began each of his killing cycles represented Trinity’s childhood lost due to the tragic death of his family. The murders that followed represented each of their deaths in sequence. First, there was the accidental death of his sister, who bled out from a cut to her femoral artery after falling in the shower. Following her loss was that of his mother, who presumably jumped to her death from grief. Finally, his father died from a trauma to the head, possibly inflicted by Trinity.

Although Trinity’s victimology was more apparent on the surface than Dexter’s, we can also see a strong link in both serial killers between their psychology and their choice in victims. Of course, this is because we have the benefit, as viewers, of insider knowledge, which includes information about both killers’ personal histories, MOs, and signatures. Combined, this information allows us to draw the most accurate conclusions regarding victimology. Most criminal investigators do not have the same benefit.

The Nail in the Coffin

We set out to discover the story told by Dexter’s crimes. Using three popular aspects of crime scene investigation (modus operandi, signature, and victimology), we were able to analyze Dexter’s criminal behaviors, psychological traits, needs, deviancy, and fantasies. If Dexter becomes sloppy, a similar analysis completed by his own police department could readily lead to his arrest. Due to frequent inconsistency in victimology and the evolution of MO over time, signature, according to some experts, can be the most useful tool for linking a series of crimes to one criminal and apprehending him.

This certainly seems to apply in Dexter’s case. Clean crime scenes, dumped bodies, and dissimilar victim characteristics leave little or no lead with regard to MO or victimology for investigators. Dexter’s signature, though, is more telling. Aspects of it, including his trophies and overkill, or excessive use of force, could be located, analyzed, and one day linked to our main character. In season two, at least one of Dexter’s signature aspects, overkill, was revealed when his bagged, slaughtered bodies were recovered from the ocean. This discovery earned Dexter the title “the Bay Harbor Butcher” but was not enough to lead to his apprehension.

In addition to the possibility of one day revealing his identity, Dexter’s signature tells his story—his traumatic life history and fantasies. As loyal viewers we sympathize with his pain and plight, and root for Dexter as he continues to foil the boys and girls in blue.

Marisa Mauro, PsyD, is a psychologist in private practice with a focus on forensics in Austin, Texas. She also works as a freelance writer and regularly contributes to her blog, “Take All Prisoners,” on PsychologyToday. com. Previously, Dr. Mauro worked as a clinical psychologist at the California Department of Corrections and Rehabilitation. Much of her work there was focused on violent offenders, gang members, and inmates serving life sentences. She has also taught as an adjunct professor and conducted research on personality, academic success, career success, eating disorders, and suicide.