Activated when a beast.
Person has claws when in beast form.
Claws are what Vincent uses to fight when he turns into a beast. The mark they make has become the signature for when he attacks someone: three cuts next to each other.
Being injected with genetically-engineered animal dna is the only known way in which a person can come to have the human-animal physiology required to develop this trait.
The claws can be used in an attack, for defense, to kill someone or simply to maim them. They can also be used to rip clothing, shread metal or tear large things apart. The claws unconciously come out when one turns into a beast.
All the soldiers who unknowingly took part in the muirfield gene-splicing medical experiment developed claws, which came into sight one they turned into beasts, after they were injected with a serum containing DNA from many different animals. No super soldier was ever seen using this trait before they were killed or went rogue.
Vincent has used his claws on many an occasion, mostly in self-defense, else to save an innocent person. They are very sharp, and he has used them, on more than one occasion, to kill.