The scientific consensus is that examinations of the sort described are both ineffective and unethical.
I found an essay from PLOS medicine, titled Forced anal examinations to ascertain sexual orientation and sexual behavior: An abusive and medically unsound practice. (Cichowitz C, Rubenstein L, Beyrer C (2018) PLoS Med 15(3): e1002536. https://doi.org/10.1371/journal.pmed.1002536)
It summarises the evidence as follows:
The earliest recorded tests purported to detect homosexuality were described by a 19th century French forensic doctor who erroneously claimed that six criteria could be used to identify homosexuality on examination [9]. Despite being published in the 1800s and discredited by medical professionals then and now, the ideas put forth continue to inform states’ practices—namely that examination of the anal sphincter can correctly determine whether or not an individual has participated in consensual receptive anal intercourse [9]. More recently, in Egypt, physicians have attempted to determine this through electromyography, sonography, and manometry of the anal sphincter, pelvic floor, and rectum, respectively [9].
and
In 2016, an independent panel of forensic experts including doctors, psychologists, and psychiatrists issued a statement unequivocally refuting all claims that anal examination can identify sexual practices [12]. The statement discredited the most commonly cited reason for conducting exams—to determine anal sphincter tone. The panel highlighted the fact that there are no standardized ways of determining anal tone with digital rectal examination, that there are high levels of normal variability within the population, and that numerous conditions may affect anal tone, independent of any practiced behaviors.
The references are:
[9]: Long S. When Doctors Torture: The Anus and the State in Egypt and Beyond. Health Hum Rights. 2008 Mar 6;7:116–40.
[12]: International Forensic Expert Group. Statement on anal examinations in cases of alleged homosexuality. Torture. 2016;26(2):85–91.
The IFEG statement is another summary.
It introduces context very similar to that quoted in the question:
Medical personnel are called
upon to conduct a digital examination of the
anus using a gloved and lubricated finger of
the examiner as well as visual inspection of
the anal area and sometime the insertion of
tubes of varying sizes. The examination is
performed with the presumption that there
are characteristic signs that correlate with
consensual anal intercourse, namely laxity of
the anal sphincter. In some cases, examiners
claim that the appearance of the anus and
the degree of laxity are signs of "chronic anal
intercourse" or "habitual anal penetration."
It states unequivocally that:
There are no scientific studies that provide
any basis for the validity of forcibly conduct-
ed anal examinations in the detection of
consensual anal intercourse.
It details five problems:
- Lack of standardised measurement and baseline data
- Normal variability in anal sphincter tone
- Lack of standardised procedure
- The potential for involuntary reaction of the inner sphincter and voluntary tensing of the outer sphincter
- A wide variety of causes for decreased anal sphincter pressure, listing the following examples
mechanical trauma,
increasing age, haemorrhoids, chronic
constipation, irritable bowel syndrome,
neurologic conditions such as pudendal
neuropathy from constant straining, cauda
equine syndrome, diabetic neuropathy,
multiple sclerosis, Amyotrophic Lateral
Sclerosis (ALS), Parkinson’s Disease,
Guillain-Barre syndrome, iatrogenic
causes (caused by physicians) such as
surgical sphincterotomy for the treatment
of anal fissures and other anal/rectal
surgeries, benign prostatic hypertrophy,
and side effects from medications.
The other reference is a long essay by Scott Long, which provides more primary sources.
The "19th Century Frenchman" referenced elsewhere is Auguste Ambroise Tardieu, who wrote a treatise called Etude médico-légale sur les attentats aux moeurs ("Forensic Study of Assaults against Decency") in 1857.
In it, he proposes six signs of "passive pederasty" (what we would now call receptive anal sex), clearly similar to those used in the Tunisian report. In Scott Long's translation, they are:
- excessive development of the buttocks
- funnel-shaped deformation of the anus
- relaxation of the sphincter
- the effacement of the folds, the crests, and the wattles at the circumference of the anus
- extreme dilation of the anal orifice
- ulcerations, hemorrhoids, fistules
Long does not cite specific refutations of this work, but quotes private correspondence with an expert:
Dr. Robert Nye, a historian of sexology, wrote to me, "The famous six 'signs' of passive sodomy were questioned and disregarded by the very next generation of forensic doctors and sexologists."
