DID the victim die of a stab wound, or was the injury inflicted after death? Existing forensic techniques are limited in their ability to determine exactly when a stab wound was inflicted, but experiments on the bodies of 64 stab victims may point to a more precise method.
It involves counting white blood cells called mast cells in and around the edges of a wound, which appear to vanish as healing begins.
Mast cells aid healing by releasing granules containing growth factors to rebuild tissue, and enzymes that destroy dead flesh. After releasing their granules, the cells lose the ability to make an enzyme called chloroacetate esterase, so they no longer show up when exposed to a dye that reacts with the enzyme.
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Manfred Oehmichen and his colleagues at the University Hospital of Schleswig-Holstein in Kiel, Germany, found that fewer enzyme-positive mast cells showed up in the wounds of people stabbed to death than in neighbouring undamaged skin. However, when Oehmichen inflicted stab wounds on cadavers, the number of these cells was the same everywhere (Forensic Science International, ). 鈥淚f a person was alive [when stabbed], you鈥檇 see a reduction in the mast cells,鈥� says Oehmichen.
