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Drug-Facilitated Sexual Assaults by LeBeau (FSC, April 1999)

Drug-Facilitated Sexual Assaults by LeBeau (FSC, April 1999)

April 1999 - Volume 1 - Number 1


Roll Call

Toxicological Investigations of Drug-Facilitated Sexual Assaults


Marc A. LeBeau
Forensic Examiner/Toxicologist
Chemistry Unit
Federal Bureau of Investigation
Washington DC

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Difficulties Surrounding the Investigation of
Drug-Facilitated Sexual Assault
Table 1
Successful Investigations


In past generations, alcohol and sedatives such as chloral hydrate were surreptitiously slipped into beverages to incapacitate an individual; typically, to commit robbery. In recent years, the idea of slipping someone a Mickey has taken a new twist with the use of drugs that are more difficult to detect, cause amnesia, and rapidly impair the victim (Andollo and Hearn 1997; Baselt 1998; Bismuth et al. 1997).

The victims in these cases tend to describe similar experiences. They often admit to having had one or more alcoholic drinks with a friend. A drink is left unattended for a period of time, after which the victim describes losing track of events and then waking in an unfamiliar environment, inappropriately clothed, or with a sensation of having had sexual intercourse. They are often confused and sleepy for hours to days following the event.

Although the majority of cases involve spiking the victim’s drink, other scenarios exist that should also be considered as drug-facilitated sexual assault. For instance, a victim may voluntarily consume recreational drugs that lead to impairment. At other times a victim may lose consciousness after mixing prescription or over-the-counter medications with ethanol. If an individual takes advantage of such a situation and has unconsensual sexual relations with the victim, it should be considered a case of drug-facilitated sexual assault.

Difficulties Surrounding the Investigation of
Drug-Facilitated Sexual Assault

Anyone who has dealt with cases of drug-facilitated sexual assault recognizes the difficulties surrounding these investigations. Problems include the vast number of drugs that can be used to commit the crime, the reporting of the crime, the collection of proper specimens, and the lack of findings in the forensic toxicology laboratory. Interestingly, many of the obstacles encountered in these investigations are directly related to the drugs used in these crimes.

Although the media has labeled drugs such as Rohypnol® and gamma hydroxybutyrate (GHB) as the date-rape drugs of the 1990s, in actuality, these are only two of the many drugs that have been used in recent years to incapacitate an unknowing victim (El Sohly et al. 1998). Table 1 lists drugs that have reportedly been detected or suspected in cases of drug-facilitated sexual assault (LeBeau et al. 1999). Of those listed, ethanol is the most common finding in investigations of drug-facilitated sexual assault. Although no other one drug is as prevalent as ethanol, benzodiazepines are present in a significant number of drug-facilitated sexual assault cases (El Shohly et al. 1998; LeBeau et al. 1999).

A number of the drugs listed are considered low-dose preparations and have synergistic effects when mixed with ethanol. Because such small amounts of the drug are required to cause sedation in an individual, it is difficult to detect the presence of the drug in a biological specimen unless sensitive methodologies are used in the forensic toxicology laboratory.

Achieving the lowest level of detection needed for these cases often requires the use of targeted analyses in which testing focuses on only one drug at a time. Needless to say, the analysis of a specimen for all of the drugs in Table 1 would prove to be a very time-consuming challenge.

The pharmacological properties of these drugs can present another problem for the toxicologist. Many of the drugs listed in Table 1 are quickly absorbed after oral administration, resulting in a rapid onset of effects. Depending on the drug or drugs used, these effects can include strong sedation with loss of consciousness, lowered inhibitions, amnesia, or combinations of these effects.

Many of these drugs are rapidly biotransformed into numerous inactive metabolites that may be conjugated. Some have very short half-lives, whereas others remain in the body for a fairly long period of time. One, GHB, is an endogenous product that is naturally occurring at low levels in the human body.

Often the reporting of the crime of drug-facilitated sexual assault becomes one of the biggest difficulties for the forensic toxicologist. Given the amnesiac effect of some of the drugs listed in Table 1, it is understandable why the victims do not report the crime for days after the alleged drugging occurred. There have been reported cases in which the victims were not aware that they had been sexually assaulted until videotapes were uncovered that showed the assault while they were sedated.

Another difficulty is that many of these drugs cause effects that are characteristic of ethanol intoxication. Unfortunately, this leads many law enforcement officers to assume that the victim was drunk and realizing the difficulties of such a case, they may delay a thorough investigation. Of course, any delay in the collection of biological evidence in a sexual assault is harmful to the toxicological investigation, so every effort should be made to collect appropriate specimens as quickly as possible.

As with any case of sexual assault, there is always the issue of the victim’s credibility. It is not surprising that the media’s recent interest in reporting these cases has led to an increase in the number of claims of drug-facilitated sexual assault. The thorough toxicological investigation required of these cases becomes very frustrating when it is later revealed that the victim was not truthful. Obtaining a full history of the case prior to performing any analyses is essential to screen out some of these cases.

Most jurisdictions have protocols for the collection of evidence from sexual assault cases. These protocols should be followed in any rape case regardless of the suspicion of drugging. However, the most important evidence in cases of drug-facilitated rape is often not collected—a urine sample. Unfortunately, most rape kits do not provide a container for urine; thus this specimen is not obtained.

Given the fact that there is usually a substantial delay between the drugging and the reporting of the crime, the urine allows for a longer window of detection of drugs commonly used in these crimes. The sooner a urine specimen is obtained after the alleged event, the greater the chance of detecting drugs that are quickly eliminated from the body. A urine specimen is probably of little value if it is obtained after four days of the suspected drugging of the victim. For an extensive analysis to be performed, it is recommended that a minimum of 30 mL of urine be collected; however, 100 mL is preferred.

Because drugs are generally detectable in blood specimens a much shorter period than in urine, blood specimens are usually useful only when the collection has occurred within 24 hours of the drugging. The blood (approximately 30 mL) should be collected in a container with preservatives (such as gray-top tubes containing sodium fluoride and potassium oxalate) and refrigerated. This blood specimen should be collected in addition to blood specimens needed for other forensic testing (i.e., serology or DNA). Although not crucial, a blood level of a drug, along with pharmacokinetic information, can assist in corroborating or disproving a victim’s version of events.

Occasionally, the victim of a drug-facilitated sexual assault vomits. Vomiting is very common after consumption of some of the drugs listed in Table 1. The analysis of the vomit may also prove useful to the investigation.

Although usually not the case, the forensic toxicology laboratory can actually be an impediment to the successful investigation of drug-facilitated sexual assaults. Because of differences in budgets, personnel, and caseloads; forensic toxicology laboratories differ in their capabilities to perform sensitive screening tests for the drugs in Table 1. Today’s push for rapid determination of common drugs of abuse in biological specimens has driven the field to rely heavily on immunoassays. Of particular concern is the fact that many of the benzodiazepines listed in Table 1 (and their metabolites) do not cross-react well with the antibodies in these assays; particularly at the levels seen in cases of drug-facilitated rape (Huang and Moody 1995; Edinboro and Poklis 1994; Morland and Smith-Kielland 1997). This can lead to many false negative results. Proper procedures should be in place to perform sensitive analyses for the drugs listed in Table 1, and detection limits for these procedures should be documented.

Successful Investigations

The successful toxicological investigation of drug-facilitated sexual assault cases is dependent upon many factors outside the control of the forensic toxicologist. Therefore, it is imperative that toxicologists when given the opportunity, educate the other members of the team (i.e., law enforcement officers, medical professionals, and victims) as to what is needed to strengthen the investigation. A number of recommendations have been presented elsewhere (LeBeau et al. 1998; LeBeau et al. 1999), but an overview of these may be helpful:

1. As soon as the crime is reported, a urine specimen (up to 100 mL) should be obtained as quickly as possible from the victim. Depending on the drug or drugs used in the crime, the urine specimen may indicate drug exposure at a maximum of four days prior to collection. Additionally, if the drugging occurred within the past 24 hours, blood specimens should also be collected and preserved.

2. Obtain as much information as possible prior to beginning an analysis. Important facts to gather include:

a. What symptoms did the victim describe?

b. How long was the victim unconscious?

c. How much time passed between the alleged drugging and the collection of the specimen or specimens?

d. How much ethanol did the victim consume?

e. Did the victim take any drugs (recreational, prescription, or over the counter)?

f. How many times (approximately) did the victim urinate prior to the collection of a urine specimen?

g. What drugs do the suspect or suspects have available to use?

h. Any other appropriate questions based on the case history.

After obtaining the history, it may steer the toxicological investigators in a particular direction. This may help alleviate some of the time-consuming analyses required in a drug-facilitated sexual assault.

3. Develop sensitive assays for the drugs found in Table 1, and know your limitations. Depending on the time of specimen collection in relation to the drugging, many of the drugs in Table 1 may require detection limits below the 10 ng/mL level. If your procedure cannot adequately determine if an individual had consumed a particular drug in the time frame dictated by a particular case, inform the investigators of this.


Reports of drug-facilitated rape are increasing at an alarming rate. Victims, accused perpetrators, medical professionals, and law enforcement officers are relying on the forensic toxicologist to conduct the best possible testing of the specimens that are available.

This article has addressed some of the more common problems encountered in cases of drug-facilitated sexual assault. It has also provided suggestions to overcome some of these obstacles.


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Bismuth, C., Dally, S., and Borron, S. Chemical submission: GHB, benzodiazepines, and other knock-out drops, Journal of Toxicology and Clinical Toxicology (1997) 35:595-598.

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