Forensic and procedural difficulties of chemical submission

The premeditated use of chemical substances to manipulate the will of people has been gaining prominence for its association with criminal practices, especially sexual aggression.

A recent article in the Journal of Legal Medicine presents a clinical case (in which it is suspected that sexual abuse could have existed under the influence of psychoactive substances by chemical submission [SQ]) that illustrates the difficulties of the forensic toxicologist to detect the presence of these substances in biological fluids, and consequently those of the Courts of Justice that sometimes only have the victim’s statement as proof of charge.

Medical Forensic Description

A 45-year-old woman was treated at the Hospital Emergency Department at 11:45 p.m. by the coroner and the gynecologist on duty. The patient reported waking up in a house next to a stranger who tried to maintain a sexual relationship with her by assaulting her in the face of her opposition. Referring, in addition, an anamnestic lagoon in the previous 3 hours. Upon inspection, two inframandibular ecchymoses and pain at the left scapular level were located. The main diagnostic suspicion was that it was a sexual assault by submission.

A toxicological screening was performed on a urine sample in the hospital, being negative. To the National Institute of Toxicology and Forensic Sciences (INTCF), vulvar, anal and vaginal area samples (for biological analysis), and blood and hair samples (for toxicity analysis) were sent. Two months later, a new sample of hair from the occipital area of ​​about 35 cm was collected and sent.

The amnesia that he referred to, of sudden onset without justifying the alcohol intake, seemed compatible with the so-called SQ and therefore the toxicological analysis sought to detect any substance that could have caused it. The results of the INTCF analyzes indicated that the semen present in the vaginal sample coincided with the genetic profile of the alleged aggressor and that chemicals related to the possible SQ or alcohol were not detected in blood or hair.


Both the Prosecutor’s Office and the private prosecution described the facts presented as constituting two crimes: sexual abuse, committed on the victim while she was deprived of meaning, and attempted violation once the woman was awake.

In the judgment (currently appealed), the court acquits for the crime of sexual abuse, for the absence of proof of lack of consent (although the sexual relationship is deemed credited by the result of the genetic comparison), while condemning the assault Sexual degree of attempt at dawn (articles 178 and 179 of the CP, in relation to art. 16 and 62). Given that the sentence acquits the crime of sexual abuse in application of the in dubio pro reo principle, it is worth mentioning at this point the difficulties of having evidence in the case analyzed. Although the picture referred to by the victim is consistent with the clinical situation caused by the drugs involved in the processes of SQ, that no related chemical substances were detected, it would not provide sufficient information.

The time elapsed from the facts to the sampling (almost 24 hours) could contribute to the physiological elimination of the substance (if it had been administered), and a single dose is hardly detectable in hair.

SQ cases pose a challenge to forensic laboratories because of the multitude of substances with similar effects, due to their rapid action and elimination of the organism, and due to the available analytical technology that in many cases is unable to detect low levels.

In our country, the performance of care services for victims of sexual assault is governed by a common protocol for health action in the face of gender violence. In 2012, the INTCF disclosed an action protocol for cases of sexual assault with suspected poisoning in which, in addition to the procedure to be followed by forensics, it was established that the delay in going to a medical center by the victim is inversely proportional to the possibilities of detecting the substances usually involved in these cases. This makes it essential for society to be aware of the existence of these toxins and the importance of attending a health center immediately if there is suspicion of involuntary intoxication, for which it is necessary to educate the population.