Sumner Redstone

Redstone, as executive chairman of both Viacom and CBS, had controlled the two companies through privately held National Amusements

Kopelson, who first met Redstone at a 2001 dinner party, said he and the media mogul became best friends and attended screening parties over the years

The issue arose as part of a lawsuit that is questioning whether Redstone knew what he was doing when he removed Viacom CEO Philippe Dauman

Herzer claims Redstone, the controlling shareholder of CBS and Viacom, wasn't mentally capable in October, when he kicked her out of his mansion and ended her oversight of his medical care