God of War 2 DEMO question - how do I stab down?

[BlackMamba]

I love the new moves (L1 + square, triangle, circle) and how Kratos has a follow-up attack after your standard "weak" attack combo (hold and release square for shoulder bash and hold and release triangle for variation on the launch into an air-combo) but does anyone know how to do the move where Kratos stabs down (from a standing position)? I did it once and I'm not sure if I can do it all the time or if it's a situation-dependant move (meaning an enemy needs to be in a certain position). Thanks.