Drug Facilitated Sexual Assault-DFSA

2021 Forensic Update on Date Rape Drugs (Drug Facilitated Sexual Assault-DFSA) Segmental Hair Shaft Testing

admin March 15, 2021 Blood Drugs

Date rape drugs are those substances that impair a person’s ability to give consent to sexual activity or incapacitate the person so that they may not resist a sexual assault regardless of ability to give consent.

A person (usually a female but sometimes a male) may become voluntarily intoxicated or involuntarily intoxicated but the end result is the same. The drug (or drugs) effect is to cause a change in the mental status of the person so that they are impaired to make the consensual decision regarding sexual activity.

Another effect may be to incapacitate a person’s ability to resist sexual advances or sexual assault by impairing their neurologic motor functions such as stance, balance, and gait rendering the person unable to locomote away from the perpetrator or physically resist them. 

Many substances can cause both effects at the same time, notably ethanol, benzodiazepines and opioids.

The list of possible date rape drugs is large. See that list in the previous Date Rape Drugs forensic update on this website. Ethanol, benzodiazepines, opioids and THC (tetrahydrocannabinol) are commonly detected in the blood and urine samples of date rape victim investigations. 1

However in many cases the victim is unable to provide a blood or urine sample within the time window the drug(s) occur in those samples. An alternative sample that extends the time window of detection is a hair shaft sample. The hair shaft collected is that portion of the hair that grows above the hair root and above the skin. (see graphic below) 

hair follicle diagram

The hair shaft is formed in the hair root, and the hair root uses nutrients from its blood supply (see red {arterial} and blue {venous} blood vessels supplying the hair root). Drugs and their metabolites present in the blood supply will be incorporated into the hair shaft as it is forming in the hair root.

Head hair is most commonly collected, a bundle of hair cut from the surface of the scalp as a contiguous bundle. Often the sample is cut from the back of the head. 

cutting hair sample

Head hair grows at different rates depending on the person. One quarter to one half inch per month is a common range of growth rates.

As an example, three inches of hair shaft sample grown at the rate of one quarter inch per month would represent one year of drug exposure contained in the hair.

A portion of the entire hair shaft bundle can be tested as a screening test to determine if any drug or metabolite is present in the hair sample. If the sample tests positive, further testing may be performed to determine the approximate time window of exposure. That testing is performed on segments of the hair shaft bundle, cut in (usually) one quarter to one half inch segments, labeled sequentially from the scalp end of the hair shaft bundle.

hair specimen

The individual hair shaft segments are analyzed and in the ideal situation all of the segments are negative except the segment in the time period of interest. If just one hair shaft segment is positive for the drug (metabolite) of interest and that segment is in the time window of the event, that test result provides evidence of involuntary drug exposure.

In fact it has been reported that using micro-segmental analysis it is possible to identify the specific day of drug exposure. (Kuwayama et al)

Test results are confirmed by mass spectrometry, similar to blood and urine confirmation testing.

Segmental hair shaft analysis provides an alternative procedure when traditional blood and urine samples are not available for timely toxicology testing in the investigation of an involuntary drug exposure case.

References:

  1. Kuwayama K, et al,  (2018) Micro-segmental hair analysis for proving drug-facilitated crimes: evidence that a victim ingested a sleeping aid, diphenhydramine, on a specific day. Forensic Sci Int 288:23–28
  2. Anna Carfora et al, Long-Term Detection In Hair Of Zolpidem, Oxazepam And Flunitrazepam In A Case Of Drug-Facilitated Sexual Assault, J Anal Toxicol., 2020 Nov 12
  3. Fiorentin, T.R., “Toxicological findings in 1000 cases of suspected drug facilitated sexual assault in the United States”, Journal of Forensic and Legal Medicine, Volume 71, April 2020, Pages 56-64
  4. U.S. Department of Justice “A National Protocol for Sexual Assault Medical Forensic Examinations”, September 2004

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