Found some info…in case others interested
https://www.yourcentralvalley.com/news/u-s-world/explainer-role-of-alternate-jurors-in-ex-officers-trial/
WHAT ARE ALTERNATE JURORS?
During the criminal trial, alternate jurors will be indistinguishable from their peers. In fact, they won’t even know they are alternates. The judge won’t reveal who the alternative jurors are until attorneys have finished making their cases. That’s so that the alternates don’t yawn off during proceedings and are ready to step in if another juror is unable to continue.
The alternate jurors will be the final two selected for the 14-person panel. Opening statements are expected March 29 unless the process isn’t complete by then.