Blood and Jail Cells

The question: If I were to receive a blood transfusion, and the next day commit a crime, and I happen to leave some blood at the crime scene, would the DNA evidence be compromised?

First of all, I think it highly unlikely that even the most dedicated criminal would feel well enough to break the law the day after a blood transfusion. Second of all, I would be very disappointed to know that there existed a person who was in need of a blood transfusion, blessed enough to actually receive one, and then thank God by committing a crime the very next day. But all that aside, we must examine the science of the question.

Human blood is composed of three types of cells: red blood cells, white blood cells, and platelets. Of these, the white blood cells are the only component that is considered complete, meaning they possess a nucleus and DNA. Red blood cells are designed to efficiently transport oxygen to the body and carbon dioxide away from the body. Platelets are not true cells, they are more like discs that have chipped off a larger cell, and are used in clotting. These two cell types do not contain a nucleus or DNA.

Blood used in transfusions usually contains only red blood cells. Therefore, in theory, none of the donor’s DNA is being imported into the recipient. And even if there happened to be some stow away white blood cells, the recipient’s immune system would attack and kill them, probably within 24 hours. So, again in theory, the recipient, also known as the criminal, could be identified using DNA evidence.

Now a bone marrow transplant, on the other hand, can cause some confusion when dealing with DNA. The development of blood cells, or haemopoiesis, originates from the stem cells located in the bone marrow. In this case, the transplanted stem cells would populate the recipient’s blood with cells containing the donor’s DNA, and since the recipient’s bone marrow has obviously failed, there would be little to none of his own DNA in his bloodstream. This situation can, and has, caused some serious issues concerning DNA evidence.

And I know that the post’s title sounds like a Wheel of Fortune Puzzle answer.