Drug-facilitated sexual assault (DFSA) is a sexual assault (rape or otherwise) carried out on a person after the person has become incapacitated due to being under the influence of any mind-altering substances, such as having consumed alcohol or been intentionally administered another date rape drug. The rape form is also known as predator rape. 75% of all acquaintance rapes involve alcohol and/or drugs. Drugs, when used with alcohol, can result in a loss of consciousness and a loss of the ability to consent to sex. Drug-facilitated sexual assault (DFSA) is a sexual assault (rape or otherwise) carried out on a person after the person has become incapacitated due to being under the influence of any mind-altering substances, such as having consumed alcohol or been intentionally administered another date rape drug. The rape form is also known as predator rape. 75% of all acquaintance rapes involve alcohol and/or drugs. Drugs, when used with alcohol, can result in a loss of consciousness and a loss of the ability to consent to sex. Researchers have found that alcohol-facilitated rape is the most common form of sexual violence against women. As with other types of rape, a DFSA is a crime of physical violence, and can be a result of sexual hedonism and entitlement. Most victims of DFSA are women and perpetrators men. Sexual assaults of men and women who have voluntarily consumed alcohol or drugs is common and not new, being mentioned in the 1938 film Pygmalion. It is also not new to slip something into somebody's drink to incapacitate them. (See Mickey Finn.) However, in the mid-1990s, law enforcement agencies began to see a pattern of women having been surreptitiously drugged for the purpose of sexual assault and rape using date rape drugs: odorless, tasteless incapacitating drugs that may produce anterograde amnesia. The female victim, participating in alcoholic drinks, whether coerced or in a mutually relaxed environment, would find herself suddenly losing awareness of her surroundings. Upon regaining consciousness, hours later, she may be in a different location, with signs having been sexually interfered with, such as missing or disarranged clothing, bruises, the presence of semen, or vaginal or anal soreness. She may feel after-effects of substance use such as wooziness, weakness or confusion, and little or no memory of what had happened to her. In some cases, her attacker may be gone; in others, he may behave as though nothing unusual has occurred, perhaps offering to drive her home or to a hospital. Most DFSAs are similar to non-drug-facilitated date rape, but not all. DFSAs may occur between employers and employees, particularly in situations where an employee is vulnerable, for example because they are an undocumented worker or for some other reason cannot risk losing their job. In such circumstances, researchers say an employer may take a vulnerable employee to dinner, and then drug and sexually assault the victim. DFSAs may also occur between landlords and tenants, or between small business owners and their clients. In those cases, researchers say the perpetrator is often socially inept, living alone, with poorly established intimacy with others.:451–456 DFSAs may occur in a healthcare context such as a dentist's or doctor's office, often for the purpose of anaesthesia. Finally, they may also occur inside families, with the perpetrator for example raping a child or a vulnerable family member. Male-on-male DFSAs occur almost exclusively in social or school settings, such as men raping foster sons, men picking up hitchhikers, and sadomasochistic killers such as Jeffrey Dahmer and John Wayne Gacy who immobilized their victims through sedation before sexually assaulting and murdering them.:454–453 Most DFSA perpetrators work alone, but some work with accomplices, including male friends, a male and female couple, and brothers. A female accomplice may be used to help gain the trust of an intended female victim.:454–453 In 1990, Canadian serial killers Paul Bernardo and Karla Homolka drugged Karla's younger sister Tammy with valium after which Paul raped her; one year later they drugged her with halothane and raped her again, after which she choked on her own vomit and died. According to law enforcement officials, DFSA perpetrators generally share four characteristics: they have access to sedating drugs and understand their effects, they have access to a setting (often a home or workplace) where the rape will not be interrupted while in progress, they are able to establish at least a small amount of trust with an intended victim, and they have a plan to avoid arrest and prosecution which may involve re-dressing the victim, telling the victim the rape was consensual or that no sexual contact took place, or exiting the premises before the victim regains consciousness.:451 Researchers say that DFSA perpetrators are opportunistic and non-confrontational. They ordinarily do not threaten, force, batter or mutilate their victims, nor do they carry weapons, steal from their victims or destroy their property. They tend not to have a history of physical violence. They are often invested in their careers or communities: they are not generally culturally marginalized.:457 Some researchers say that DFSA perpetrators are highly sexually interested but unable to find sexual partners, and are motivated solely by sexual desire. Others say some perpetrators (who may record the rape for later viewing) are motivated by the idea of dominating and controlling somebody for sexual purposes. Researchers differ over whether perpetrators are satisfying an actual compulsion. Some believe there is little evidence to suggest the urge to commit DFSA is uncontrollable, while others say the 'astonishing frequency' with which some perpetrators repeat the offence suggests some degree of compulsion. All DFSA perpetrators have a very high likelihood of reoffending.:454–457 The stereotype of DFSA perpetrators is that they are personable, clever and attractive. This is sometimes but not always true.:454–457 There is no evidence to suggest that DFSA perpetrators network among each other, either online or off, although they can sometimes be found on sites where the effects of recreational drugs are discussed.:458 Because drugging the victim makes it possible to easily overpower him or her, it is possible for perpetrators to commit DFSA quite late in life, and researchers say some perpetrators are over the age of 60.:454–457 Different types of drugs and alcohol have different outcomes in terms of the body's consciousness, but all drugs inhibits the ability to consent. This experience can often be traumatic to DFSA victims . One study of general population American women who believed they were victims of DFSAs found 81% knew the alleged perpetrator before the rape. A similar study focused on college students found 83% knew the alleged perpetrator before the rape.