The main defendant in the case seeks to invalidate his confessions, claiming that the investigation was conducted without Mandelblit's (the ex-Attorney General) approval and that undue pressure was exerted on him that led to the signing of the state witness agreement.

The investigation into the submarine affair was intended to incriminate the Prime Minister, Binyamin Netanyahu, and despite this, it was conducted without the approval of the Attorney General. 

In order to achieve this goal, undue pressure was applied to Mickey Ganor and the investigators made him sign a state witness agreement based on false representations. This is what Ganor's defense attorneys, attorney Amit Nir and Ravita Tzemach, claim (4.8.23) in their arguments at the trial in the case.

NEWSRAEL: It seems that many important "state witnesses" are recanting and turning into witnesses against the prosecution by claiming (with strong evidence) that they were pressured, their families were threatened in order to agree to charges against Netanyahu.

As such - Trump, who by an amazing coincidence is facing also a group of indictments is doing the right thing by challenging them.