A Delaware judge has ruled that CBS will be allowed to use a secretly recorded video of aging mogul Sumner Redstone as part of the discovery process in its lawsuit against controlling shareholder National Amusements Inc., but the video will be kept under seal and out of public view.

Judge Andre Bouchard of Delaware Chancery Court granted a CBS motion to compel documents from NAI related to changes on the board of directors at Viacom in 2016 as well as changes made by NAI to Viacom’s bylaws in 2016. CBS’ larger goal is to raise questions about the mental capacity of Sumner Redstone and bolster its argument that Shari Redstone, daughter of the 95-year-old media titan, has improperly been calling the shots at the company that her father controls. NAI owns Redstones’ controlling stakes in CBS and Viacom.

To make the case regarding the discovery motion, CBS submitted a video of Sumner Redstone recorded at his home in January 2018 by CBS director Arnold Kopelson. NAI had sought to have the video stricken from the discovery process, saying it was recorded without the mogul’s knowledge. CBS filed the video under seal, which keeps it out of the public record in the case.

CBS included the video to support its contention that Sumner Redstone did not provide written answers to questions submitted to him as part of the discovery process. The judge granted CBS’ motion to strike those answers, but he did not approve CBS’ request that Sumner Redstone be deposed as part of the case.

CBS issued a statement casting Wednesday’s ruling as an important victory for its discovery process. A rep for NAI declined to comment.

“We are very pleased with the court’s ruling today, which will now allow us to conduct appropriate discovery from NAI on the issue of who controls NAI, and will also give us a full opportunity to obtain highly relevant documents relating to NAI’s coup against the Viacom Board in 2016,” CBS said in a statement. “With respect to the videotape of Sumner that was submitted to the court under seal, we are pleased that the Court, while keeping the tape confidential, recognized today that the tape is relevant to the issues in this case.”

Bouchard also presided over a flurry of lawsuits involving the Redstones and NAI when Shari Redstone implemented changes at Viacom that led to the ouster of chairman-CEO Philippe Dauman. At the time, CBS Corp. chief Leslie Moonves was supportive of Shari Redstone’s moves given the deterioration of Viacom under Dauman’s leadership. But now the Viacom situation from 2016 is front and center of CBS’ effort to issue a special dividend to shareholders that would have the effect of diluting the Redstones’ voting power in CBS from about 80% to about 20%.