We're dealing with a creature from the canidae family that's over two hundred years old.

 (Excerpt Alma Introduction)

 

“Look at the results and at what happened to the blood samples that were added to the OO Negative.  The samples were drained of all their nutrients and healthy cellular functions before it too turned OO Negative.  However, with the blood samples added to the OO Positive, they weren't drained.  They were immediately converted to OO Positive and instead of being depleted of red and white cells; they increased in numbers.”

            “So OO Negative takes away and OO Positive adds to the blood it comes into contact with?” he summed up.

            “Da.”

            “And the blood sample taken from the latest corpse I brought in, is OO Negative?” he checked.

            “Da.”

            “Then how does OO Positive come into this investigation?”

            "The blood under the nails of the latest victim is the perpetrator's blood," she said.  "And guess what kind of blood type the murderer has?"

            "OO Positive?"

            "Da."

            "So the latest victim has OO Negative blood and the murderer has OO Positive blood?" he clarified.

            "Da, but Griggori, all your victims in this murder spree are OO Negative.  Yet, they all tried to fight off their attacker, which explains the blood under their long nails.  The blood that I've taken from each of the victims nails are OO Positive."

            "So it's the same perpetrator?"

            "Da, but look, this OO Positive suspect has the same DNA which was taken from three other corpses which were autopsied 236 years ago.”

            He watched as she hit a new command into the touch-screen.  Three faces appeared on the screen, a man and woman whose heads were barely attached to what was left of a ravaged neck.  The third victim which was a middle-aged male had a singed hole in his chest where his heart used to be.

            “Who are these people?” he wondered.

            “They couldn't be identified so they were simply called Jane Doe and John Doe.  Their deaths were written off as a wild animal attack from the nature of the bite marks on the youngest male and female's necks.   The older man’s death was by being impaled with a long, sharp, metallic object such as a sword.  But the Police declared him dead possibly by the same perpetrator because of the claw marks on the rest of his body.  The clawing and teeth marks were concluded to be from a species in the canidae family."

            "They thought wolves did this?" he arched an eyebrow, sceptical.  

            She nodded, "But see here, the DNA retrieved from the bite marks?”

            “It’s the same as our OO Positive blood type," he squinted at the screen.

            “These three victims and the ‘animal’ that supposedly attacked them, all had OO Positive blood," she sighed.  “But look at the year that the victims died, 2145 AD.  The DNA of the murderer who killed them has the same DNA taken from our latest victims.  We're dealing with a creature from the canidae family that's over two hundred years old."