How would you respond to the accused suspect's denial of having the blood type you identified, since he has proof that he had just received a blood transfusion with type o blood?

In humans, the blood group is determined by the substances on the surface of the red blood cells, called antigens. Blood groups are grouped into systems. In the ABO system, there are four possible blood groups: A, B, O and AB.

Group O can be for everyone; it is called the "universal donor". Thus, among other things, blood O will be used in emergency situations, and in the case of impossibility to perform an isogroup transfusion.

Type O blood can be given to anyone since it doesn't have any of the activators like type a and b have