Prosecutors and Cooperating Witnesses

Question is about whether prosecutors can - legally or ethically - pressure a witness to give incriminating testimony about someone when there’s no other evidence of guilt beyond what they themselves just squeezed out of the guy.

For example, suppose they’re investigating an accounting fraud at some company. They have emails and/or testimony incriminating the CFO, but nothing whatsoever indicating that the CEO was aware of it. Can they tell the CFO “we’re ready to offer you a plea bargain on such-and-such terms, but only if you’re prepared to ‘cooperate’, and ‘cooperate’ means implicate the CEO in the crime”?

Or if they’re investigating a murder and they find some guy with likely knowledge of the facts with some drugs, can they tell him “we’re prepared to offer you a plea on the drug charges, but only if you ‘cooperate’ in the form of testifying that so-and-so did the murder”, if there’s no actual evidence of that guy’s involvement beyond this testimony?

Or can they only pressure the cooperating witness to give this testimony if they already have other evidence of guilt and are only looking to add to it and make it stand up in court?

I appreciate that they’re much less likely to get a guilty verdict if all they have is this type of testimony. But my question is whether there’s any bar at all to them doing this to begin with. (I suspect there is not.)

[This is inspired by recent developments in the Trump-Russia story, but is a more general question so I hope responses can avoid getting bogged down in the specifics of that case.]

It wouldn’t be ethical if they thought they were encouraging false testimony. It is ethical to say, in essence, “We’re trying to get this guy. We think he’s involved. If your cooperation can help us convict him, we’ll go a little easier on you.” If that is truly all they have on the target, conviction might be difficult. (but I’m sure it happens)

IANAL but… a lawyer in any position - defense or prosecutor - legally cannot suborn perjury, cannot ask for testimony they know is false. I would assume this extends to willful blindness, asking for testimony they oughta know damn well is not true. (Of course that’s a grey area that may fall to the law license board to decide). So during interrogation if they get something they know they can’t use, why bother? Because the devil is always in the details. OK, you claim the CEO knew. When di you tell him? What was his reaction? Why do the following emails give no indication of this? Why does he keep asking about X in his emails if he knows the answer?

For example, Martha Stewart was NOT convicted for insider stock trading. Yes, the CEO of the other company called her a bit before she dumped her stock. But neither side revealed what was in the conversation. Instead, they got her for obstruction for what she said to investigators that was incorrect. (They did threaten to ruin the lives of some of her lowly paid employees also and drag them through years of court cases, bankrupt them with lawyer fees, if she did not plead guilty…)

The point is, the prosecution needs (should need?) more than just the word of the perpetrator. Especially if that person is the instigator and main actor. The question would be if there were additional evidence to support the claim. (i.e. you told them the stock would tank combine with - they sold the stock immediately after; or in the Russia case, it would involve a plethora of email chains. If someone habitually conversed with email but there is nothing in email to corroborate a claim, that would be odd. )