Which Cop Show has one not appeared in?

A Serial Killer is defined as someone who commits multiple murders, out of some kind of mental or sexual compulsion, in separate incidents with at least a few days in between killings. This is their "cooling off" period, when they temporarily lose the compulsion to kill, and distinguishes them from Spree Killers, who kill in much more regular intervals of weeks or days, if they don't simply go on a murderous rampage that usually ends only when someone captures or kills them. The minimum death toll to be classified as a serial killer is 3-5 people, providing they were killed in separate incidents over a period of more than 30 days. If numerous people are killed in a single incident (e.g. someone murders an entire family in their home), that is mass murder, though mass murderers can and do become serial killers if they act multiple times.

It's worth pointing out that actually getting convicted of the three to five murders is rare. Historically, being convicted of one murder was generally enough to get you executed and pretty quickly as well, with no need or opportunity to prove the rest. Even with large-scale abolition of the death penalty, there's not much point in a prosecutor spending lots of money on multiple charges when just one will probably get the killer a life sentence unless proving multiple charges or other aggravating factors can overcome the barriers to the death penalty. Of course, the killer could be deemed insane or kill themselves before the trial.

Real Life serial killers are usually divided into 4 categories but motives may significantly overlap and fictional killers tend to fall into one or more of these categories as well, if not by design, then by their nature.

• Visionary — The killer suffers a break from reality, delusions, and/or hallucinations, that compel them to murder. They might believe God or Satan, or simply voices, are telling them to kill, or that killing will prevent some kind of disaster. Tends to result from some kind of trauma and/or a mental illness like schizophrenia. The Insanity Defense will usually only apply to this type (though even this only counts if their mental illness impaired their sense of right and wrong), and as such if a killer is going for that defense, they will usually claim to be such — this very rarely works in Real Life, and in fact is very rarely attempted, probably because in practice there is only so much difference between being locked up in a jail cell for life for multiple murders, and being locked in an insane asylum for life for the same.
• Mission-Based — The killer believes that their actions are for the greater good, or in the service of some higher purpose, because they are performing some kind of social, political, philosophical, or religious service, generally targeting people they blame for society's ills, or view as sinful, distasteful, or dangerous. Though they may be deluded, they are not psychotic like the Visionary killer, having a rough grasp on reality. Vigilante killers are a sub-type of this.
• Hedonistic — Someone who kills for lust, thrill, or comfort/profit. The first two kill principally because they enjoy it; lust-based killers get sexual satisfaction out of murder, while thrill-based ones simply find it exciting. Comfort/profit killers are the type who kill to maintain or fund a life of luxury, or otherwise for money; hitmen and assassins fall into this category, but it usually refers to cases of fraud, embezzlement, or robbery that involves killing somebody. Women serial killers are usually comfort killers, though not all comfort killers are women.
• Power/Control — These murderers kill because it makes them feel powerful. Often (though not always) the type who were mistreated or abused as children, they are driven more by insecurity or rage than by any pleasure they might get out of killing, though that might eventually play a part. If rape is involved, it is not, like a Hedonistic killer, motivated by lust, but as another means of dominating the victim. Very often involves torture, and/or binding the victim in some fashion, though neither of these are requirements.

Incidentally the majority of Real Life serial killers fall under hedonistic with some power/control, most killing to satisfy a (usually sexual) fantasy. In addition, as mentioned, there are several sub-types of these killers that fit into the above categories. Some examples include:

• Revenge killers commit murders to lash out at real or perceived wrongs done to them in life, the victims typically being substitutes for the perpetrator of the original offense. May kill friends, relatives, or strangers for slights, sometimes petty in nature.
• Black Widow killers cash in on the insurance of murdered relatives (or friends with wills). Typically serial spouses who murder their new husbands/wives and then move on, though they have been known to murder other relations, including children. Almost always women.
• The Bluebeard killer is a male counterpart to the Black Widow killer, except that this specifically refers to men who kill their wives, not other relatives. Also, the motive is usually power, not financial gain, though that often plays a part.
• Professional Killers are now increasingly regarded as a sub-type of serial killers, falling under Comfort/Profit Hedonistic killers.
• Cost Cutters are those who kill to save money, such as a person who murders employees to avoid paying them.
• Lethal Caretakers are nurses, carers, or other such who kill patients and carees for profit, e.g. to cash in on social security checks in their name. Usually women.
• Angels of Death are similar, but kill patients for feelings of power and control, or sometimes serial mercy-killing (or believe their crimes to be such), and are thus harder to trace. Again, usually women, though Harold Shipman — British doctor and arguably the most prolific serial killer in the world — falls into this type.
• House Cleaners are Mission-based killers who target prostitutes, the homeless, petty criminals, minorities, political enemies, and anyone else they view as blights on society, with the aim of "improving" their community by getting rid of their perceived unwanted or undesirable elements.
• Sexual Sadists are lust killers who torture their victims before killing them; the torture is usually more important than the actual murder. The torture may be psychological and can last for a matter of seconds or minutes, or it can last for hours or days or even longer, depending on the offender.
• Antisocial killers are those suffering from a severe case of Anti-Social personality disorder. Impulsive and impatient, they pathologically violate social norms and values, such as repeatedly committing serious and petty crimes. Serial murder is usually just one of many crimes they regularly commit, and they often do so in the course of other crimes, such as robbery, assault, rape, torture etc.
• Cannibalistic killers hunt down people so they can eat their flesh. Typically this is done either out of a belief that by consuming the victim they can take on some of their traits, or because they are disdainful of the victim and wish to prove their dominance over them by reducing them to food. Jeffrey Dahmer is a well-known real life example of this type. Hannibal Lecter is the most iconic fictional example.
• Münchausen by Proxy is a personality disorder where the perpetrator harms another for attention — for example, murdering a relative for sympathy at the loss, or killing someone and then trying to "save" them to act the hero. Usually not killers, but serial abusers of relations or strangers, but have been known to turn lethal.
• Police killers are serial murderers who are also involved in law enforcement. There's a roughly equal chance that they're a Vigilante Man who thinks he is cleaning the street by killing criminals and anyone else they regard as immoral, or just an indiscriminate psycho who butchers people for fun while using their jobs as covers for their crimes.
• Cop Killers are the other way around, killing actual police either decent policemen or foul, they kill with the belief that they are above the law and out of vengeful vendettas against law enforcement for real or imagined slights.
• Supernatural Killers are what happens when a normal, flesh and blood killer for any of the above types dies. Or rather, doesn't. He may discover Evil Makes You Monstrous, get turned into a vampire or werewolf, or linger on as a ghost. Alternatively, he may be a mortal with magical powers from a demon, or a spectre who needs to kill to keep control of his host, or almost anything paranormal as long as he has to keep killing. This usually makes them (perhaps literal) nightmares, as they suffer from a Horror Hunger, gain superpowers, and are nigh unkillable. This is one kind of Resurrected Murderer.
• Murderers who invoke Serial Killings, Specific Target kill additional victims to disguise the motive for their intended victim's murder and make it look like the work of any of the other types of serial killers described above.

Serial killers can further be divided into Organized, Disorganized and Mixed. Organized killers plan their crimes carefully and often well in advance, and are thus always premeditated. They try to maintain a high level of control over the crime scene and bring with them the items they use to incapacitate and kill their victims. They may even hold a stable job and have a good education, and appear perfectly normal in every way. Such people are very likely to be The Chessmaster. The latter are much more impulsive and careless; their crimes may or may not be premeditated, and they are recklessly executed when they are (often with a random weapon) without due care for witnesses or leaving evidence. These tend to be poorly educated, unemployed or without steady employment, have no or very few friends, and a known of history of mental illness. Mixed have traits from both categories. However, some serial killers descend from organized into disorganized (reasons include overconfidence or seeking more extreme methods for satisfying their sick desires if they've gotten bored with their usual method) or vice versa (a killer may find a more satisfying method or be getting more skilled).

Many potential Serial Killers get caught quickly because they use an MO that makes their crimes easy to detect and identify, have such a strong compulsion to murder that they literally cannot stop themselves even when they know they are under suspicion and/or police surveillance, or (often mixing with the former) have such a twisted perspective that it simply does not occur to them that they're leaving evidence behind, or by collecting trophies or the bodies of victims. Some may even taunt police as if it were a game and derive further thrill from it. Exceedingly few Real Life serial killers actually want to be caught, and even these few are mostly invoking an extremely twisted form of It's All About Me and No Such Thing as Bad Publicity; they want to be seen as extraordinary.

The following things tend to occur in a serial killer plot:

• The killer sends a note to the police, or a newspaper, or both, with a taunting message that ends in a challenge along the lines of "You can't catch me." A gruesome souvenir may also be included.
  • A variation is to have the killer send a message saying "Please catch me before I kill more."
• Serial killers are often, but not always, portrayed as The Chessmaster, brilliantly layering one Evil Plan onto another. Often, this takes the form of a series of Batman Gambits that lead the police on a series of wild goose chases as the killer gloats.
• They have a wall full of newspaper clippings covering their actions. Sometimes they keep a photographic record of their kills, or even a souvenir of the victim's.
  • Scenes of the killer watching news reports about their own crimes, and gloating about being in the media spotlight, are also common.
• If it's part of a Story Arc, one cop is probably going to fall victim (which is part of the requisite Tonight, Someone Dies hype).
• At the climax, one of the cops is usually Alone with the Psycho, but is saved Just in Time.
• If the killer is not depicted as Ax-Crazy, then the victims all have something to do with one another.
• If somebody else is wrongfully implicated, and looks close to taking the rap, the serial killer will bump them off, even though this means casting suspicion back on himself.
  • Or the killer will kill again while the wrongfully accused is incarcerated, casting suspicion back on himself.
  • Sometimes he will do it because it casts suspicion back towards himself, because he is insulted that the police suspect someone he considers unworthy of the attention.
• The killer might leave a distinctive Calling Card at each scene of his crimes.
• The killer might be a Poetic Serial Killer, who kills bad people with ironic methods.
• Or they're a Theme Serial Killer, and they have a set of themes (possibly taken from a poem/book), with each victim fitting the next theme in the killer's list (which they rarely get to complete).
• The killer may try to use the same weapon for his murders, like a knife or a certain model of gun.
• The killer will fondly recall or talk about their victims.
• Some of these plots have the Serial Killer insert themselves into the investigation, either by posing as a witness, victim, or in some cases, an investigator. The killer's purpose in doing this is either to misdirect the police or prove how much smarter the killer is than the cops. While it's much more common in fiction, this has actually happened in real life.

Serial Killer plots tend to be men killing women, although there are rare inversions. This is somewhat realistic, however, because in the real world, the vast majority of serial killers are men — or, more exactly, men tend to murder in ways that make it easier for them to get caught. Female serial killers will typically be Angels of Death and may work in health care or similar vocations. In fiction, they'll often have a Torture Cellar or do their killings in a Sinister Subway.

Daytime soaps have had an unusually high number of serial killers. One Life to Live has had at least two in as many years. It's the chic way for producers to pare down their casts.

It's notable that many of these behaviors are realistic for serial killers, though seeing all of them with one killer is unlikely. Also notable is the fact that they are practically never allowed to go uncaught by the end, despite many of the most famous unsolved cases in history being serial killer investigations.

Sometimes they are more like a so-called Spree Killer, i.e. someone who goes on a murderous rampage in a smaller area over a shorter time. In fact, this is more common than actual serial killers, though characters often confuse the two, as time constraints mean the killings in a story usually take place over the space of a few days, whereas real serial killers by definition usually have weeks, months, or years between their kills.

The term "serial killer" isn't actually that old; it was coined in German (as "Serienmörder", serial murderer) in 1930 by Ernst Gennat, the highly influential director of the Berlin criminal police in the 1930s. "Serial murderer" crops up in 1966 and "serial killer" is generally attributed to FBI agent Robert Ressler in the 1970s, it didn't enter popular culture until 1981.

Indirect Serial Killer is a Sub-Trope that involves serial killers who kill people indirectly.

A counterpart to the Serial Rapist; it's not uncommon for the tropes to overlap, such as with the real life Ted Bundy. Compare with Psycho for Hire, where a job that requires killing people is used by villains to act out their sadism. See also Hunting the Most Dangerous Game, where someone makes an actual sport out of killing people. The killer feared by other killers is a Serial-Killer Killer.

Serial killers are very much Truth in Television, but we must ask that real life examples not be listed here — there are plenty of examples of them on Wikipedia. noreallife

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