The reflectiveness of human skin is somewhat hard to duplicate, but graphics engineers have been perfecting modeling it for years and years to make more lifelike humans in computer generated images.
Most likely, you simply need a dummy which has similar subsurface scattering to that of human skin.
This company seems to achieve this effect using silicone, but again, testing would be required, and such realism is overkill to fool a laser beam.
Something simpler could be done -- you simply need three layers of material which each have the same reflective component as the three layers of skin.
