Thanks for the summaries.
As HDG notes, the generics' burden to prove obviousness is by "clear and convincing evidence," and such standard is a higher bar than the lower "preponderance of the evidence" standard. To the extent the generics may succeed in proving obviousness with respect to a given patent claim, that claim would be invalidated, rendering moot the relevance of Amarin's attempting to prove infringement of that claim.
Also as noted, Amarin's burden is to prove infringement (of a claim that the generics are unable to invalidate), and the standard for proving infringement is by a "preponderance of the evidence," generally defined as being "by the greater weight and degree of the credible evidence," or "51% of the evidence."
For Amarin to win, the generics must fail in their burden to invalidate any claim (i.e., fail to prove the claim invalid due to obviousness) that Amarin also succeeds in proving is infringed by the ANDA label. Any one such combination (regarding the same claim) of result would mean Amarin would win.