A summary judgment motion is a legal motion that can be filed by either the plaintiff or defendant in a civil case (after a lawsuit has been filed); with civil injury cases, the defense usually uses this motion as their "weapon of choice" to claim there "is no case to be decided by a fact finder, or jury."  Meaning that the injured party has no legal claim because of "x, y, z," or more specifically, the injured party has shown no issue of disputed material fact.  

For example, if someone took a drug that caused them injury, and the injured person had no real evidence to show the drug caused him or her injury, then a defense lawyer would file the summary judgment motion asking the judge to dismiss the claim because the injured person has no sufficient evidence to even base a claim to be decided by a jury or judge.  Thus, there is no real "causation of injury."