Medico-legal importance of genetic markers

1. Identification of a person:

• This could be done from blood, semen, (cases of rape), saliva which may be found on bites, cigarette ends at scene of crime, and chewing gum, as well as hairs found at scene of crime or held in hand of victim.

2. Identification of remnants:

• As in mass disaster cases where bodies can be reconstructed.

3. Disputed paternity:

• This arises in the following conditions

• When husband denies that he is the father of the child.

• In cases of rape or if child is born out of lawful marriage and the accused person denies.
• When a woman pretends pregnancy and delivery and adopts a child for sake of inheritance.

• Paternity can be excluded by ABO grouping alone in about 16 %
• Addition of MN system raises exclusion of paternity to 33% to rise to 59% with addition of Rh,
• Serum proteins typing raises exclusion to 76% to reach to 89'% when red cell isoenzymes are added. Exclusion reaches 98.5% of testing when a number of HLA systems are done. Exclusion rate using HLA typing alone is 80%.

4. Disputed maternity:

• This occurs when children are mixed in hospitals and two mothers claim one child. Mitochondrial DNA fingerprinting is done

5. Before blood transfusion:

• To avoid mismatching in ABO system and developing Rh antibodies in an Rh -ve person given Rh +ve blood. A second transfusion with Rh+ve blood leads to serious transfusion reactions.

6. Rh-ve mothers giving birth to Rh+ve babies

• She should be given preparations of antibodies to Rh antigen at labor or shortly after to prevent developing of erythroblastosis foetalis in the second baby. This is done by removing any Rh+ve fetal cells that may have entered the mother's blood stream.

7. In threatening letters for blackmailing or life threats. Examination of the envelop may reveal traces of saliva from licking the envelop or stamp. Examination of genetic markers can point to the assailant.

8. In sex crimes

• Identification of assailant could be done by examining semen for grouping (if he is secretor) as well as for DNA

Category: Forensic Medicine Notes