Letter from University Hospitals of Cleveland\u27s Rh (blood) lab director Roger Marsters, Ph.D., who describes the tests conducted on the blood stains lifted from the wristwatches of Sam Sheppard and Marilyn Sheppard.
According to Marsters, the tests concluded that the blood stains on both watches were of blood group M and likely came from Marilyn Sheppard because her blood was also of blood group M.
The possible presence of another individual who might have blood group M would modify this presumption according to whether s/he had lost any blood and other circumstances
