What does Knowingly cause murder mean, for a imate?

Answer 1

Because proving intent can be so difficult, they use a lower standard...that is, if you knew or should have known that your actions would lead to the death of another, that's good enough for proof (of mens rea).

Answer 2

Knowingly = with the knowledge that the result was substantially certain to occur.
Keep in mind that this includes the higher culpable mental state of Purposely (which means with the intent to cause the required result of the crime).