Question related to sharing

You can hide the detail layout of the case from the target user going to the court trial.

  1. Create a formula field, is courtgoing User Current user where formula is

    $User.Id= Court_Going_User__c

  2. Use Component visibility of lightning on your detail page layout, enter image description here

and only display detail layout when is court going user current user is false. enter image description here

  1. Also, you can also add a text area to tell the user that you cannot access the case data. enter image description here

You don't have to worry about sharing , Your org seems to be LDV org so sharing table would be extensive, and altering the sharing table having millions of records is slow.

I agree List views would be pain, but if you show non sensetive information in them you can probably save yourself from sharing hell.