Examination of Firearms Review: 2007 to 2010 - Interpol

sperm-free vaginal swabs and saliva. Sakurada et al 18 used the PRM2 gene together
with the semenogelin 1 (SEMG1) to show the presence of semen in a stain. Both
genes are being expressed in semen, however also 2 out of 5 urine samples showed
some expression, but this is presumably caused by semen contamination of the
urine.
The same as with blood microRNAs can be used for semen identification. Hanson et
al 16 reported two miRNAs (miR-135b and miR-10b) that can be used to differentiate
semen from blood, saliva, and vaginal fluid. Zubakov et al 15 reported five miRNAs
(miR-135a, miR-10a, miR-507, miR-891a, and miR-943) that have high expression
levels in semen relative to blood, saliva and vaginal fluid. Of these miRNAs only
miR-891a is human specific.
3.4 Other body fluids
Although other body fluids such as saliva, urine and vaginal fluid are encountered
less frequent than blood and semen in forensic practice the unambiguous
identification of these fluids can be of great value in certain forensic cases. The
traditional method for identifying saliva is based on the detection of the alpha
amylase enzyme. The classic test for urine is based on the detection of urea an
organic compound that concentrates in urine. Both the amaylse test and the urea test
are relatively insensitive and not specific for the body fluid of interest. At present
there is no specific and sensitive presumptive test to screen for the presence of
vaginal secretions. The coming availability of specific RNA tests for the identification
of these body fluids will therefore be of great value for the forensic identification of
these body fluids.
3.4.1 Saliva
The genes that can be used to identify saliva are statherin (STATH) and HTN3 12,18 .
Both genes were not detected in blood, semen, and vaginal fluid. The HTN1 gene
was also detected by the HTN3 primer and therefore showed some false positive
results in semen 2 . Zubakov et al 13 concluded with five possible markers for saliva 13
(SPRR3, SPRR1A, KRT4, KRT6A, and KRT13) SPRR3 and SPRR1A show no
detectable expression in semen, and the remaining three (KRT4, KRT6A, and
KRT13) show vast over-expression in saliva compared to semen. However the
markers could not differentiate saliva from vaginal fluid, due to the complex nature of
vaginal fluid. In addition, the markers could at least be identified in 6 months old
stains. Furthermore Zubakov et al 13 remarked that tissue identification should not
only be based on the presence of certain body fluid markers, but also on the absence
of the other body fluid markers. In 2009 Hanson et al 16 were the first to use miRNAs
for forensic body fluid identifications. For the differentiation of saliva from blood,
semen, and vaginal fluid they concluded that miR205 and miR658 could be used 16 .
Besides a molecular biology approach saliva can be identified using a lateral flow
immunochromatographic strip test. This test is a part of the Rapid Stain Identification
test (RSID TM ) and is developed to detect the presence of salivary α-amylase. The
detection limit of this test is 1µL of human saliva, and takes about 10 minutes to give
a result.
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