What is the burden of proving a cause of action has no merit?

A defendant moving for summary judgment bears the burden of showing that a cause of action has no merit because plaintiff cannot establish an element of the claim or because defendant has a complete defense. The burden then shifts to the plaintiff opposing the summary judgment motion to establish that a triable issue of fact exists as to these issues. (Saelzler v. Advanced Group 400 (2001) 25 Cal.4th 763, 768.)