How are the face cuts done when Dexter takes his blood samples of his victims?

Question

Whenever Dexter has his victim on the slab ready to be killed, he cuts them with a surgical knife and takes a blood sample. Obviously the knife is fake and the blood is fake but quite often you will see the knife touch the skin and the fake blood comes out, emulating a cut on the cheek.How is this effect done?

Answer 1

Simple. It's CGI.