Secretors are individuals whose blood group antigens are present in bodily fluids like saliva, while non-secretors only express antigens on tissues like red blood cells. The ability to secrete antigens is genetically controlled. Various tests can identify bodily fluids like saliva, semen, and blood found at crime scenes. Detecting antigens in fluids can help identify victims or perpetrators, solve disputed parentage cases, and provide evidence in crimes where fluids are present. A combination of precipitation, gel diffusion, immunological and other tests are used to analyze fluids for evidentiary value in forensic investigations.

1. Secretors
Dr. Pratapsingh Rathod

2. What are Secretors?
Secretors are individuals who secrete their ABO antigenic charteristics (A,B,
and H Blood group substances) into the body fluids.
• 80% of people secrete these agglutinogens in the body fluids as water
soluble form.
• Non secretors are individuals who posses only lipodal form of this
agglutinogens.
• In Non Secretors blood group antigens are usually present over tissues
like RBC’s epithelium

3. Inheritance of Secretors:
• The ability to secrete soluble antigens is under control of a pair of
genes, Se and se.
• Se being dominant over se
• If the Se allele is inherited as Se Se or Se se, the person is called a
“secretor”
• If the Se allele is inherited as se se, the person is called a “non
secretors”
• The Se gene is responsible for the expression of the H antigen
on glycoprotein structures located in body secretions
• Secretors express soluble forms of the H antigen in secretions that
can then be converted to A or B antigens (by the transferases)
• The se allele is an amorph (nothing expressed)
• se se individuals do not convert antigen precursors to H antigen
and has neither soluble H antigen nor soluble A or B antigens in
body fluids.

4. Lewis System in Secretors:
Lewis blood group system is based on expression of glycoprotein
called Lewis(Le) antigens on surface of red blood cells or body fluids or
both.
-- Lewis ( a- b+) phenotypes are Secretors and Lewis (a+ b-)
are non-Secretors, where a and b allelic forms of Le gene.
Testing a known body fluid sample for ABO and Lewis groups
usually allows a conclusion with regards to ABO group and Secretor
status i.e., whether an individuals ABH blood group substances should
be found in evidential body fluids or not.

5. Body Fluids:
There are a many different types of body fluids that are secreted, they
can be broken down in two categories:
1. Excreted
- Sweat e.g., Assault,
- Breast milk
- Faeces ( often covered by mucous membrane)
- Bile
- Vomit
- Aqueous Humor
- Sebum (skin oil)
2. Secreted
- Cowper’s Fluid (Pre-ejaculatory Fluid)
- Semen
- Saliva
- Nasal secretions
- Female Ejaculate
- Urine
- Tears

6. Analysis of Body fluid:
• Body fluids are useful in helping forensic scientists and pathologists to
put together a detailed picture of how an individual died and likewise
may also present means of identifying the perpetrator.
• Varying fluids can be found contained within the human body and
about the body of an individual who has been the victim of a crime
• When dealing with a crime a scene that may have body fluids
secreted , all the personnel must be fully clothed in protective clothing to
avoid contamination of crime scene.
• Chemicals and ultraviolet light can be deployed to uncover the
existence of these body fluids in circumstances where they might be
overlooked or not visible to naked eye.
• These fluid if detected at a crime scene are swabbed, bagged and
collected in vials, which are air tight and at low risk of cross
contamination.

7. Tests:
Tests to identify body fluids:
1. Precipitin test: This test detects proteins present in human
secretions.This test is useful in detection of saliva, milk, blood and
semen

8. 2. Gel Diffusion Test:
In this test antigen (Specimen) and antiserum for human antibodies in placed in
two wells in agar plate.
Diffusion of antigen and antibody occurs in agar and percipitin Bands will
develop between the wells

9. 3. Double diffusion in agar gel:
A piece of stained material or extract is placed in a central wells
surrounding with six wells containing a drop of antiserum specific for a
globulin.

10. 4. Immunological method :
It detect Prostate specific antigen(PSA, p30) a glycoprotein produced by
prostate present in urine and Semen

11. Other Tests:
a) Precipitation- electrophoresis test
b) Latex test
c) Isoenzyme methods
d) Tests for seminal specimen
- Florence test: It detects Choline present in seminal fluid
- Barberio’s test : It detects Prostatic secretions
- Acid phosphatase test: It detects acid phosphatase present in
prostatic secrerion in seminal fluid
- Creatine Phosphokinase: It detects creatine phosphokinase
present in spermatozoa
- Immunological method: It detects MHS-5 produced from
seminal vesicles and Mab 4 E6 present on sperm cells
- Choline and spermine test: It detects Choline and Spermine
present in Semen

12. Tests to Determine ABH antigens:
1. Tube Method
In this method a drop of specimen is added with antisera of A,B and
H in separate tubes, agglutination is seen by naked eye.
2. Tile Method
In this method a porcelain tile is used instead of tubes

13. 3. Absorption – Inhibition method
In this method samples and antisera are allowed to react with each
other for a longer period
4. Mixed Agglutination Test
In this test stained cloth is cut into 2-3mm pieces, fibers are separated and
added to tubes containing antisera of A, B, H types, Antisera will form clumps
over cloth fibers
5. Absorption-Elution
Technique
This technique is similar
to mixed agglutination,
but clumps are seen on
the walls of the test tubes
6. ELISA

14. Medico-Legal Importance:
1. Identifying Blood groups in Disputed maternity or paternity as a
first order exclusion
2. Identification of victim or offender where only available specimen
is either saliva, urine or semen
3. Identification of mutilated remains where saliva or sweat sample
can be obtained
4. Sexual crime, samples like saliva of the offender can be obtained
5. In extortion or abduction cases, saliva samples can be obtained
from envelopes, face masks, nasal secretions, saliva from cigarette
butts
6. Alcohol intoxication with assault vomit samples of offender can be
helpful in identification