Already at the time of publishing his discovery of the blood groups in 1901, Landsteiner pointed out that the blood-group reaction could be used for investigating the origin of a blood sample, for instance of a blood stain.
The use of blood-group determination in paternity actions also constitutes a significant advance in this field, even though the proof is of a negative character.
However, a blood-group determination does not give results suitable for use as evidence under all circumstances.
If, for instance, the blood of a blood stain is from an individual belonging to blood group A, then it cannot be from an individual who is found to belong to group B, but a blood-group determination will not tell us from which person of blood group A the blood came.
A blood-group determination can, in fact, never establish paternity, but can exclude the possibility of it.
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