When Does it Become Prosecutorial Abuse?

So, granted that prosecutors regularly charge people with minor matters like perjury or income tax evasion when the real, underlying crime is too hard to prove, when does it become an abuse to do so.

When is it an abuse to charge a suspect with something other than the real, underlying offense, either because the real underlying offense is, though morally offensive, is not actually a crime, or because the real offense is too hard to prove?  And some Trump supporters are currently saying any time it is done:

They’re trying to Al Capone the president. I mean, you remember. Capone didn’t go down for murder. Elliot Ness didn’t put him in for murder. He went in for tax fraud. Prosecutors didn’t care how he went down as long as he went down. The same goes for Democrats. Whatever avenue is needed to bring down the president, they’ll take it.

The clear implication here is that if there was not sufficient admissible evidence to charge Capone with murder, then charging him with a lesser but more provable crime was dirty pool.  A critic caustically comments:

You might wonder why Trump’s supporters believe his legal defense is aided by analogizing him to a murderous criminal. Perhaps the answer is that Capone had several qualities that recommend him to the Republican grassroots base. He was a business owner — or, in modern Republican lingo, a Job Creator. He was an avid Second Amendment enthusiast. And, most importantly, Capone, like Trump, was a victim of the deep state.

Most people, I think, would agree that stopping Al Capone was a worthy goal and if a little legal trickery was called for, then it was well worth doing.  Capone was, after all, guilty of sin of tax evasion.  Should he be given immunity from prosecution for tax evasion simply because he was guilty of much worse as well?   That doesn't seem logical.

More realistically, there are some things that are technically crimes but almost never charged as such.  A charge under a technical crime usually means that there is something else afoot, more serious but harder to prove.

Hillary Clinton's e-mail server has been used as an example.  Sending State Department e-mails on a private server does meet the technical requirements of mishandling of classified information.  People have been prosecuted for mishandling classified information.  But usually there is something more than just mishandling.  James Comey explained:

All the cases prosecuted involved some combination of: clearly intentional and willful mishandling of classified information; or vast quantities of materials exposed in such a way as to support an inference of intentional misconduct; or indications of disloyalty to the United States; or efforts to obstruct justice.

If you want a classic case of prosecutorial misconduct (and under a Democratic administration no less) the classic case would be the case of Wen Ho Lee, who was prosecuted on simple charges of mishandling classified information.  Wen Ho Lee was a Taiwanese-American scientist as Los Alamos Labs, suspected of spying for the Chinese.  In fairness to the "Justice" Department, the Chinese really did obtain classified information, Lee really did have access to such information, and he really did mishandle classified information, i.e., he stored it on an unclassified, though secure system.  However, the investigation found clear evidence before even bringing charges that Lee could not have been the spy for China, since the information provided include materials that lee did not have access too.  Lee was nonetheless indicted on 59 counts and held in solitary confinement for nine months.  He ultimately pleaded guilty to one count and was released, with apologies from the judge.

So, the obvious difference between the case of Wen Ho Lee and the others was that in Lee's case, although his actions were technical crimes, there was no other, more serious crime that the government lacked evidence to prove.  Or rather, there was such a crime (spying for China), but the evidence was overwhelming that Lee was not the guilty party. 

So, the short version is, if there is a serious underlying crime that is difficult to prove, prosecuting on a less serious, but easier to prove crime is not an abuse of power.  Prosecuting on a technical crime out of resentment, or just to throw one's weight around is an abuse of power.  Admittedly, there are gray areas, when the government believes there is a serious crime, but the obstacles to prosecution are not just strict rules on admissibility, but genuine weakness in the evidence.  Such cases exist.  But Al Capone was not one of them.  Neither were Spiro Agnew or Paul Manafort.  As for Flynn and Cohen -- I suppose we will see.