Sumner Redstone's granddaughter won't be permitted to join his former companion as a petitioner in a lawsuit challenging his mental competency, though she will be a witness in the trial.

A Los Angeles Superior Court judge on Wednesday denied a motion by lawyers for the former companion, Manuela Herzer, to add the granddaughter, Keryn Redstone, as a co-petitioner in the case, according to lawyers for both Ms. Herzer and Mr. Redstone.

Ms. Herzer is claiming that Mr. Redstone lacked mental competency when he threw her out of his mansion and removed her last October as his health-care agent in the event he becomes incapacitated. Ms. Herzer was replaced as health-care agent by Viacom CEO Philippe Dauman. Mr. Redstone's lawyers have argued the suit is without merit and have been fighting it. A trial is set for May 6.

Mr. Redstone, 92 years old, controls 80% of the voting stakes of both Viacom Inc. and CBS Corp.

On Wednesday, Ms. Herzer's lawyers also withdrew their motion to have Mr. Redstone examined by a neurologist.

However, the judge did grant Ms. Herzer's lawyers a victory in deciding he would allow them to expand the time period in question for considering Mr. Redstone's competency. If they successfully argue that Mr. Redstone lacked competency last October and invalidate the change in health-care agent that happened at that time, then a more recent health-care agent change could also be deemed invalid. On April 4, Mr. Redstone named his daughter, Shari, as his health-care agent, replacing Mr. Dauman.

"Philippe never asked to be health-care proxy," said a Viacom spokesman. "He just did it for his colleague and friend." A spokeswoman for Shari Redstone declined to comment.

The most recent change in health-care agents came about in the midst of settlement talks earlier this month, though the change was made separately from those discussions. The settlement talks ultimately broke down.

In a declaration filed Tuesday, Keryn Redstone accused her aunt, Shari Redstone, of threatening to kill her and pushing for a "do not resuscitate" order for Mr. Redstone against his wishes. The spokeswoman for Shari Redstone said the claims were false.

Write to Keach Hagey at keach.hagey@wsj.com

 

(END) Dow Jones Newswires

April 21, 2016 00:15 ET (04:15 GMT)

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