It's one thing for a president to declassify a document and retain it.
Irrelevant. 793 Espionage Act does NOT depend on any classification regime. DNI damage assessments, if there is an indictment, will be the primary factor in the severity of punishment and/or fines.
It's another for a Senator at the time to steal a classified document from a SCIF and retain it for many years.
An accusations of 'theft' cannot be presumed. We must wait for the Special Counsels report.
There is no statute of limitations for theft of classified documents.,
Assumes theft. If it is determined the documents were obtained inadvertently, via staff mismanagement, it is doubtful the DOJ would prosecute, UNLESS the President or VP obstructs the government in the return of the documents.
even if he became president after the crime.
If there was any Mens rea on the part of anyone it is Joey Biden.
The issue is what is the DOJ's policy on indicting a member of the executive branch regarding classified documents.
It is my understanding that they would only prosecute if 1. Docs were obtained willfully/intentionally and with knowledge of their potential damage. 2. If they obstruct the government's efforts to have the docs returned.
On #1, we have Trump on tape declaring 'it is okay for a president to take classified documents'. and on #2, he was served with a search warrant, which would only have been issued but for his refusal to return documents.
Given the above, Trump is the only one whose actions qualify for prosecution.
Mens rea ~~ In criminal law, mens rea is the mental state of the crime committed and the legal determination of a crime may depend upon both a mental state and actus reus, like the designation of a homicide as murder is a matter of intention to commit a crime or in some jurisidctions knowledge that one's action would cause a crime to be committed.
Wikipedia
Trump refused to return the documents, resulting in a search warrant. That fulfills '
actus reus'. Trump admitted on tape that he believes it is okay ot take classified documents, in defiance of 793 Espionage act. That demonstrates
mens rea. As president, it is not logical he was unaware of their potential damage. With Trump, all the elements of 793 have been met. "In my opinion" and, as always "IANAL"