By mixing blood samples with anti-A or anti-B we can see if clumping occurs and we can therefore identify the person as A, B, AB or O type. Group O is the most common with 47% of the population while AB is the least common with 3% of the population.
To carry out the tests we use cards that have the antibodies impregnated onto their surface. The control contains neither antibody and should not form blood clots with any blood sample.

Try the following exercises

A blood sample from Stephen was obtained and tested to determine his blood type. Click to see the test.
What is Stephen's blood type according to the ABO system?
Peter is blood type "AB" while Irene is blood type "B". Can both Peter and Irene give blood to Stephen? Explain.

Blood was found at the scene of a crime. The sample was tested back in the lab. Click to see the test. What percent of the population has this particular blood group?

A car was found on the side of the road at 12.30 am on Saturday. Blood was found on the drivers seat and on the steering wheel. It was obvious that the driver had sustained severe injuries. The sample of blood collected at the scene was tested at the forensic laboratory. Click to see the test. On Sunday the local hospital reported that a patient had reported to casualty at 3 am with severe head injuries. This patient needed an immediate blood transfusion and was given 3 litres of blood type "A". The patient later died. Police investigations revealed that the patient was indeed the driver of the vehicle found by the side of the road. What do you think was the cause of death? Based on the information presented to you, can legal proceedings be brought against the hospital?
A postmortem was conducted and the coroner reported that massive clotting of the patient's blood was clearly visible. How do you explain this?