PHILADELPHIA — In a filing to a judge last week, state prosecutors argued why they should be allowed to proceed with a trial for Graham Spanier, the former Penn State University president accused of child endangerment in the Jerry Sandusky sex-abuse scandal.

Spanier’s lawyers countered that the memo did nothing more than “sling mud” through “page after page of unproven, sensational allegations.”

But identifying that so-called mud isn’t possible because prosecutors filed their response under seal and inaccessible to the public.

Jeffrey Johnson, a spokesman for the attorney general, said the office filed the document under seal “in accordance with an earlier sealing order” by a previous judge in the case.

Prosecutors did the same when they answered dismissal arguments from Spanier’s co-defendants, former Penn State administrators Gary Schultz and Tim Curley.

Pennsylvania’s Superior Court in January threw out the most serious charges against Spanier, Curley and Schultz. They included obstruction-of-justice, conspiracy, and perjury charges against Spanier and Schultz and obstruction and conspiracy charges against Curley.