The term sadism is derived from the name of a French author who lived from 1740 to 1814, Donatien-Alphonse-Francois de Sade, better known as the Marquis de Sade. In 1898 Krafft-Ebing recognized the practice as a sexual perversion consisting of strong impulses to coitus, coupled with prepatory acts of maltreatment, even murder (necrophilia, then called lustmurder"), which occurs primarily because of an inability to be satisfied with coitus. Though Sadistic personality disorder was never formally admitted into the Diagnostic and Statistical Manual of Mental Disorders or DSM researchers continue to use its criteria.
DSM research criteria
Sadistic personality disorder is a pervasive pattern of cruel, demeaning, and aggressive behaviour, beginning by early adulthood, as indicated by the repeated occurrence of at least four of the following:
Most sadists like torture more than they like sex, and it is customary to refer to the three D's of sadism in this regard -- Dread, Dependency, and Degradation -- or in other words, the desire to create fear in the victim, make the victim completely helpless (dependent on the sadist), and humiliate the victim.
A sadist is clinically defined as a person who demonstrates a long-standing maladaptive pattern of cruel, demeaning, and aggressive behavior towards others. Symptoms include: a period of activity of at least six months, recurrent, intense sexually arousing fantasies, sexual urges, or behaviors involving real acts (not simulated) in which the psychological (humiliation) or physical suffering of a victim is sexually exciting. In criminology, sadism is often inferred from carefully examining crime scene behavior, and it's a common pattern (Sadistic aspect) linking many crimes. In forensic science, wound pattern analysis tends to point to evidence of sadism or not. As with many sexual crimes, victimology is important, and where rape shield laws prevent inquiring into the victim's sexual history, a 24-hour timeline will have to be used. There are essential two (2) elements that constitute the actus reus of sadism:
Sadistic and masochistic behaviour was known before Krafft-Ebing. In 1498, the Italian philosopher Pico della Mirandola described a man who needed to be flogged before he could have sex (Farin 1990). In 1639, the German physician Johann Heinrich Meibom introduced the first theory of masochism (Meibom  1718) : Based on the contemporary understanding of anatomy, he postulated that flogging the back warms the semen in the kidneys, which causes sexual excitement once it reaches the testicles. Kristian Frantz Paullini modified this in 1698 so that warm blood, not semen, descends from the kidneys, but the basic theory remained unchallenged until Krafft-Ebing. Also, sadomasochism as a sexual practice was well known in literature before the works of the Marquis de Sade. The Kama Sutra, dated roughly at the 4th century AD, describes consensual erotic slapping. In his autobiography Confessions , the French philosopher Jean-Jacques Rousseau described his unhappiness at his masochistic fantasies. Unlike other practices that were previously classified as perversions such as homosexuality or zoophilia, there is no explicit taboo of sadomasochistic behaviour in the Bible.
Krafft-Ebing published his first version of the Psychopathia Sexualis, a collection of bizarre sexual case histories and sex-crimes, in 1886. The terms "sadism" and "masochism" were introduced in later editions. "Sadism" was taken from what Krafft-Ebing knew of the life and writings of the De Sade (important parts of Sade's work, such as The 120 Days of Sodom, were only published later). Sade had died in 1814. For "masochism", Krafft-Ebing chose the name of a contemporary, the Austrian author Leopold von Sacher-Masoch. "Sadism" and "masochism", however, stem from quite different logics of sexuality and erotism, as do Sade's and Sacher-Masoch's work (Gilles Deleuze has exposed this point in his presentation of Sacher-Masoch). Krafft-Ebing's basic assumption was that all forms of sex not directly related to procreation were perversions. He described sadism and masochism in terms of the theory of degeneration as published by Bénédict Morel. This stated that characteristics such as perversions can be inherited (Morel 1957). In other words, people who engage in what was considered amoral or damaging sexual behavior -- such as masturbation -- could pass these tendencies on to their children, leading to a steady deterioration of humanity's gene pool. This theory has been disproven. Krafft-Ebing saw a basic and natural tendency in men towards sexual sadism and a natural tendency of women towards sexual masochism, a view that would be expanded by psychoanalysis. Other contemporary researchers doubted Krafft-Ebing's findings or suggested modifications. The British physician Havelock Ellis noted that enjoyment of pain was restricted to an erotic context. In 1892, Albert von Schrenck-Notzing introduced the term Algolagnia as an alternative form of description (Schrenck-Notzing 1892). However, Krafft-Ebing's theories were adopted by Sigmund Freud and became an integral part of psychoanalysis, thereby ensuring their predominance.
Freud and psychoanalysis
Freud made masochism and -- to a lesser degree -- sadism core parts of psychoanalysis. In Three Essays on the Theory of Sexuality he called the tendency to inflict and receive pain during sex "the most common and important of all perversions". He also pointed out that both tendencies commonly occurred in the same individual. Freud changed his theories on the genesis of sadism and masochism repeatedly, first stating that masochism only arose as a form of sadism against the self. He later introduced such concepts as "primary" and "secondary" masochism and sub-forms such as "feminine" and "moral" masochism. He also saw guilt as an important factor and integrated both tendencies into his theory of psychosexual development. Put shortly, they were assumed to be a sign of incomplete or incorrect sexual development in the child. Freud's followers such as Carl Jung, Wilhelm Reich and Theodor Reik expanded and modified his ideas, creating new terms and concepts in the process. Helene Deutsch postulated that all women are masochistic by nature (Deutsch 1930), reinforcing Krafft-Ebing's and Freud's views. Some theorists claimed that the population of whole countries such as Japan should be considered masochistic in a psychoanalytical sense (Nakakuki 1994). Because of these modifications, even the most basic words such as "masochism" have acquired so many different meanings in psychoanalysis that the terms have become confusing for psychoanalysts themselves and incomprehensible to outsiders (Maleson, 1984). Freud's theories on sadomasochism and the philosophy of Sade fascinated thinkers such as Gilles Deleuze and Simone de Beauvoir. Their writings, though not grounded in formal research and sometimes far removed from real-life sadomasochism, strongly influenced popular views of the subject in the mid-20th century.
Outside of psychoanalysis, views on sadomasochism began to change in the late 20th century with the study of actual behaviour of real-life sadomasochists. Sadomasochistic tendencies in both genders were noted by Alfred Kinsey as part of his reports. The first researcher to describe the existence of a sadomasochistic subculture was Robert Litman in 1972. The first large-scale empirical study on sadomasochism was conducted by Andreas Spengler in 1977. Spengler, a German physician, used questionnaires to gain basic data. His results contradicted most earlier work, especially that of the psychoanalysts, leading him to conclude that previous research was "heavily burdened with prejudice and ignorance" (Spengler 1979). When Norman Beslow expanded on this, he found only five previous empirical studies in all scientific literature, including Spengler's. Beslow was also the first to show that non-prostitute women make up a significant part of the sadomasochistic subculture. No empirical study has found a connection to violent crimes or evidence for an increased tendency towards sociopathological behaviour in sadomasochists as had been generally assumed since Krafft-Ebing. The realization that far more people than previously assumed practice sadomasochism and that sadomasochists form subcultures led to an influx of researchers from outside medicine. The anthropologist Paul Gebhard described sadism and masochism in a cultural context. Again in Germany, Thomas Wetzstein conducted a large-scale study of the local subculture from a sociological viewpoint, confirming Spengler's results and expanding on them. One major change effected by these studies was the realization that women do not limit themselves to a masochistic role. Much of this modern research is less concerned with what causes sadistic and masochistic urges than describing their mechanisms and characteristics.
The results of the empirical studies and an increasingly tolerant attitude towards sexual minorities led to more and more sadomasochists forming public groups, for example the Eulenspiegel Society in 1971. This is especially true in countries where sadomasochism between consenting adults is legal such as Germany  or Norway . As a result, sadomasochism became much more present in mainstream western and Japanese culture.
Sadism and its shades
Sadism and masochism, in the original sense, describe psychiatric disorders characterized by feelings of sexual pleasure or gratification when inflicting suffering or having it inflicted upon the self, respectively. Sadomasochism is used in psychiatry to describe either the co-occurrence of sadism and masochism in one person as separate disorders, or as a replacement for both terms, depending on the theory used. The results of the newer studies led to calls to abolish sadism and masochism as disease categories, arguing that the truly pathological forms are adequately covered by other diagnoses. The sadomasochistic subculture added a political dimension to this drive with claims of discrimination and by pointing to the precedent of removing of homosexuality from the list of mental disorders . In response, the American Psychiatric Association modified the criteria for sadism and masochism in the DSM dated 1994 so that consensual sadomasochistic behaviour alone is not considered a sexual disorder anymore. The terms are now formally reserved for severe personality disorders. In 1995, Denmark became the first country to completely remove sadomasochism from its classification of diseases. How sadism and masochism develop and why some people find these practices pleasurable remains unclear. Current theories include childhood experiences, endorphin-based mechanisms, learned behaviour, genetic dispositions, and simple conscious choice. Why consensual BDSM and pathological sadomasochism as defined by DSM share some of the same superficial characteristics is also unknown.
One of the aspects of sadism is anger, but this should be at least as evident as sexual gratification. The intention is to hurt, degrade, defile, or destroy the victim. Sexuality and power are accompanied by anger in the service of sexual gratification. By contrast, an anger-retaliatory rapist is just interested in anger, not so much sexual gratification. However, for a sadist, the aggression is eroticized. They take pleasure in the torment, anguish, distress, helplessness, and suffering of their victims. Victim selection is usually on the basis of the victim being a symbol of someone they want to punish. Age, appearance, and occupation are typical victim selection categories. Sexual sadism is similar to serial killing in that the aspect of fantasy-reenactment cycle is the same.
Sadist Serial Killers
Examination of the case studies published on male serial killers reveals that the majority of those known to us violated their victims sexually. Given the frequent reference in the academic literature as well as the popular media to serial murderers as "psychopathic sexual sadists," the author examined the extent to which clinical criteria for Antisocial Personality Disorder and Sexual Sadism were met by a sample of serial murderers whose cases were documented in the journalistic, academic, and law enforcement literatures. Criminal investigators will attest that, in general, the greater the psychopathology of the offender, the more distinctive his/her criminal behaviors tend to be. This may be plausible given the repetitive nature of sex-related offenses. Research indicates that a reliable basis from which to predict violent behavior does not exist beyond the increased probability that an individual who has been violent in particular circumstances in the past will be violent in the future given the same conditions. (Monahan, J. 1981). The repetitive nature of sex-related serial murderers may, as such, render these offenders somewhat more "predictable." Patterned behaviors such as those observed in sadistic encounters can be used to develop investigative profiles of the kind of person most likely to have committed a given series of crimes. _
Most serial killers are classified as "organized offenders." The organized offender is usually above average in intelligence. He is methodical and cunning. His crime is well thought out and carefully planned. He is likely to own a car which is in good condition. The crime is usually committed away from his area of residence or work. He is mobile and travels many more miles than the average person. Fantasy and ritual are important to the organized type offender. He selects a victim, which he considers the "right" type, someone he can control (either through manipulation or strength), usually a stranger. Most of his victims will share specific traits. He is considered socially adept. He uses his verbal skills to manipulate his victims and gain control over them until he has them within his "comfort zone." The organized killer is fully cognizant of the criminality of his act and takes pride in his ability to thwart the police investigation. He is likely to follow news reports of his crimes and will oftentimes take a "souvenir" from his victim as a reminder, that may be used to relive the event or augment the fantasy surrounding the killing. For the organized offender the souvenir constitutes a "trophy." He is excited by the cruelty of the act and may engage in torturing the victim.Sexual control of the victim plays an important part in this scenario. The organized offender usually brings his own weapon to the crime scene and avoids leaving evidence behind. He is familiar with police procedures. The body is often removed from the crime scene. He may do this to "taunt" the police by leaving the corpse in plain public view, or to prevent its discovery by transporting it to a location where it will be well hidden. (Geberth, 1990) The series of criminal behaviors of this type of offender are suggestive of an individual with an antisocial personality disorder to the extent that repeated behaviors are immoral and marked by pronounced irresponsibility. His essential problem appears characterologic in nature. He appears to lack remorse or shame and is seemingly lacking in empathic response to others. This is the type of offender who was the focus of this research._ The offenders in this study displayed aggressive and antisocial behaviors during their childhood which escalated and took on elements of sexual sadism in adulthood. There was also a style and pattern to their killings which involved domination, control, humiliation and sadistic sexual violence. The murders were committed without the least sense of guilt or shame and the killers displayed a total lack of remorse. The victims were chosen at random and the murders carried out in almost an obsessive manner. According to Hare (1993) "If you are dealing with a true psychopath it is important to recognize that the current prognosis for significant improvement in his or her attitudes and behavior is poor." (p. 205) According to Monahan (1981), "The repetitive nature of sex-related serial murderers may, as such, render these offenders somewhat more predictable." The application of such criteria could allow for the identification of potential serial killers and, hopefully, lead to proper assessment of future dangerousness and treatment strategies. According to DSM "When Sexual Sadism is severe, and especially when it is associated with Antisocial Personality Disorder, individuals with Sexual Sadism may seriously injure or kill their victims.”
Differences between a Sadist and a Psychopath
It's important to note the difference between a sadist and a psychopath.
Sadism and Necrophilia
Necrophilia is similar to sadism in that the offender may or may not care about whether the victim is unconscious or not, but sadists usually prefer them alive, and necrophiliacs prefer them dead. Sadists tend to have some rather unique, bizarre rituals that aren't even described in the abnormal psychology books yet. In this sense, they are similar to the thrill-oriented hedonist in the Holmes Typology of serial killers. As seekers of new experiences and kicks, they are constantly expanding the horizons of their sexual misadventures. In addition a necrophiliac would fit as a lust-oriented hedonist because concerned with sexual experimentation after death.
Sadism and Rape
It may be helpful to review the different types of rapists, the so-called Groth typology):
Although the latter type is also known as the sadistic rapist, a rapist is usually not sadistic in the clinical sense. Most books admit that the sadistic rapist is the rarest type. Rape is a common crime committed for most of the common causes of crime in general such as low self-control, impulsivity; lack of respect for society's rules; deficient social skills; and a tendency to lose control, especially under the influence of alcohol or drugs. By contrast, a sexual sadist is always in control. Rapists are also usually much younger than sadists. Rape is a crime committed by 12-24 year olds. Sadists tend to be in their 30s or older, and have a different pattern of behavior development. For this reason, some rapist typologies only recognize two types: power and anger.
What Sadism is not
There are many routine criminal behaviors, like rape, that are often mistaken for sadism. Harassment, Threats, Intimidation, and Terroristic threats, for example, are not sadism. Crimes of "hot" or "cold" blood are not sadism, nor are those crimes motivated by revenge. Not all acts involving postmortem mutilation indicate sadism.