I’ve seen references not only to blood being on the Shroud but that it’s type AB blood. Other blood analyzed recently from two weeping icons in Italy and in the well-known bleeding Host miracle at Lanciano, Italy, also came up with AB blood. If anyone is faking each instance of Jesus’ blood, they sure are doing a good job keeping it consistent. This Catholic chooses to believe.
There is no blood on the Shroud: all the forensic tests specific for blood have failed18 (although some investigators19 unrigorously concluded that blood was present after conducting numerous forensic tests for iron, protein, albumin, etc., which came up positive because these materials are indeed on the Shroud in the form of tempera paint). Old blood is not bright red, and no amount of bilirubin20 can explain that away. Real blood mats on hair, and does not form perfect rivulets and spiral flows. Real blood does not contain red ochre, vermilion, and alizarin red pigments. Real blood and its organic derivatives have refractive indices much less than red ochre or vermilion, and they can be easily distinguished using Becke line movement under a light microscope. McCrone's examination of the red particles on the Shroud samples revealed no blood or blood derivatives.
http://www.freeinquiry.com/skeptic/shroud/as/schafersman.html
I thought it was AB negative, which is incredibly rare. It also is the same blood type as that found on the Sudarium of Oviedo.