Sexual Examination Kit with combs
Swabs
Swabs
Principles of forensic sampling
Avoid contamination
I mentioned earlier about ‘cross
contamination’ and how to avoid it. The sampling should be done with gloved
hands. It is recommended that gloves should be changed after sampling each body
orifice and surface. These used gloves should be used as a separate
production. It is also advisable to wear
protective over cloth and a face mask if the examiner feels that he /she would
cough or sneeze. However this may not be practical in our set up.
Preparation
The doctor should have discussed
the kind of samples he should obtain with the police officer before he starts
collecting them. Therefore, it would save time if samples are pre-labelled.
Double swabbing
This technique involves swabbing
with a moist swab first and then with a dry swab. The swab should be moistened
with sterile water first and then roll over the area to be swabbed. Immediately
after that a dry swab is rolled over on the same area. By this way the dry
biological material gets loosened up and absorbed by the second dry swab. These
two swabs can be labelled A and B to show the sequence of swabbing.
Rolling over the swab
The whole of the swab head should
be rolled over the area to maximize the surface area.
Number of Swabs
Minimum of two swabs are used on
each site, one wet and one dry or if the area is moist two dry swabs. If a
stain remains even after two swabs being taken, the swabbing should be repeated
until the stain is completely removed.
Control for water and swab
The doctor should remember to
take a sample of water (into a dry swab) and a dry swab as control samples.
Packaging and Labelling
These samples should be properly
bagged, labelled, signed, sealed and handed over to the police. (Ideally
‘tamper-proof’ bags should be used.
The samples to be
taken in different types of sexual assaults
Vaginal Intercourse
After sexual intercourse
spermatozoa and/or seminal fluid can be deposited on the vulva or in the
vagina. Spermatozoa can be identified in the vagina swabs taken from
post-pubertal women up to about 7 days after vaginal intercourse. Two or more days after vaginal intercourse
spermatozoa are more likely to be found in the endocervical swabs than vaginal
swabs. It is reported that spermatozoa were found up to 10 days after vaginal
sexual intercourse in the endocervix.
The following samples should be
taken even if the patient is menstruating or has douched/washed/showered after
the incident. The current recommendation
in the UK is that these samples should be taken if the patient complains of
vaginal sexual intercourse during preceding 7 days or anal intercourse during
preceding 3 days.
a. Cut
the matted pubic hair or swab the stained pubic hair.
b. Loose
hair and other material on the pubic hair should be removed with a single use
disposable forceps.
c. Comb
pubic hair with a comb over a paper sheet. The comb and the folded paper sheet
should be taken as a production. Cut 10-20 pubic hair as control sample.
d. Two
swabs (A & B) from vulva and perineum. If the stain or skin is dry use the
double swab technique.
e. Two
swabs (A & B) from the low vagina (3-5 cm into vagina or lower half or
third of vagina). If the vagina is dry the first should be moistened with
sterile water.
f.
Ideally an appropriately sized speculum should
be inserted to lower half or third of vagina and take sampling from the vaginal
wall and fornicies using two dry swabs, one at a time. The speculum should
lubricated. If a speculum cannot be inserted two dry swabs, one at a time,
should be passed further into the vagina than the previous swabs and sample the
high vagina.
g. If
the vaginal intercourse has occurred 2 or more than 2 days prior to examination
and a speculum can be passed. Two dry swabs, one at a time, should be inserted
through the speculum and sample from the endocervix.
h. Speculum
should be taken as a production or it should be swabbed.
Anal intercourse
Spermatozoa can be identified
from anal/rectal swabs taken up to 3 days of anal intercourse even when defecation
occurred. As in the case of vaginal samples they should be obtained even if the
patient defecated, washed or showered.
a. Cut
or swab the perianal hair if appeared stained with secretions.
b. Foreign
material including hair removed with disposable single use forceps
c. Two
swabs should be taken from the perianal skin (3 cm radius from the anus), first
wet and the second dry. (Perianal swab)
d. Two
swabs, first wet and the second dry, inserted through the anal orifice (2-3 cm)
and sample the anal canal. (Anal canal)
e. Ideally
an appropriate sized proctoscope is passed 3 cm into the anal canal and swab
the lower rectum and anal canal using two dry swabs, one at a time. (Rectum). The proctoscope should be
lubricated.
f.
If it is not possible to pass the proctoscope
two dry swabs, one at a time, should be passed into the anus and sample the
anal canal and lower rectum. (Rectum/anal canal)
g. Proctoscope
should be retained or it should be swabbed.
Oral sexual act
Oral sexual act may include oral
contact with vulva/vagina (cunnilinngus), anus (anilingus) or penis (fellatio).
If there is allegation of
anilingus or cunnilingus within preceding two days swabs should be taken from
vulva, low vagina and perianal region if the patient has not washed during that
time. It is reported that swabs from skin may give positive results up to two
days (DNA from deposition of saliva.)
After fellatio spermatozoa can
persist in the mouth for two days. The following samples should be obtained if
allegation of oral penile contact during preceding two days.
a. Two
swabs from the whole of the mouth including tongue, floor, teeth, gum and
cheeks. (mouth)
b. ‘Sterile
water mouth wash’ into a polypot. (put some sterile water into the alleged
victim’s mouth, ask her/him to gurgle thoroughly and put into a polypot.) (mouth
washing)
c. Sample
of sterile water used to obtain the mouth wash is taken as a control sample.(control
mouth wash)
If the patient is the subject of
fellatio the following swabs should be obtained.
a. Two,
first wet second dry, swabs from coronal sulcus (coronal sulcus)
b. Two,
first wet second dry, swabs from glans penis (penis-glans)
c. Two,
firs wet second dry, swabs from the shaft of penis (penis-shaft)
Other general forensic samples
Depending on the circumstances
other forensic samples may be requested by the police both from the alleged
victim and the suspect. They may include:
a. Head
hair (combed, cut and plucked)
b. Any
loose material from head hair should be collected before combing using a forceps
c. Nail
scrapings and clippings from both hands. Scrapping is done first using ‘tooth
pricks’ or pointed dry swabs. Then nails are clipped, ideally with disposable
nail clippers. In our facilities a clean sterilized pair of scissors can be
used. All fingers of one hand are scrapped on to a single sheet of paper and
the ‘prick’ and the paper is collected as a production. Likewise alls the
fingers of one hand is clipped on to a single sheet of paper and the ‘clipper’
and the paper is collected as a production.
d. Wet
and dry swabbing of the stains on the skin, hands, fingers etc.
Suspect
In addition to the general
forensic samples following samples may be obtained from the suspect.
1. Pubic
hair can be swabbed or matted hair can be cut
2. Collection
of loose hair and other material from the pubic hair
3. Two,
first wet second dry, swabs from coronal sulcus (coronal sulcus)
4. Two,
first wet second dry, swabs from glans penis (penis-glans)
5. Two,
firs wet second dry, swabs from the shaft of penis (penis-shaft)
6. Undressing
and collection of clothing should be done in the same way as in the case of
alleged victim
(These lecture notes were prepared from two books
1.
The physical signs of child sexual abuse, an
evidence-based review and guidance for best practice, March 2008, Royal College
of Paediatrics and Child Health.
2.
Clinical Forensic Medicine, 3rd
Edition, Ed. W.D.S. McLay, 2009, Cambridge.)
Priyanjith Perera
12/12/12
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