Et tu, Cohen? Ex-aide Could be Tip of Trump Iceberg

New York: Michael Cohen's transformation from loyal retainer promising to take a bullet for Donald Trump to Judas spotlights the strong arm of the US law and how determined the president's former attorney is to limit his time in prison.

For more than a decade, Cohen was Trump's personal lawyer and fixer, privy to multi-million-dollar deals and two purported secret lovers, whose claims could have potentially sabotaged his boss's 2016 election.

Then Cohen hung Trump out to dry, sensationally testifying under oath in a federal court that the president directed him to break campaign finance law, while pleading guilty to bank and tax fraud.

As if referencing the enormity of his predicament, Cohen told the judge that the previous night at dinner he had indulged in a Glenlivet 12 on the rocks despite the Scotch not being his usual meal-time tipple.

Publicly Trump has denied doing anything wrong and mocked his former aide. Michael "The Rat" Cohen is how one person close to the president privately described him, a CNN journalist has reported.

So what next?

Implicating the billionaire commander-in-chief in a federal crime was a stunning move from a close former ally, signalling a willingness to cooperate with prosecutors and potentially lower his prison term, experts say.

"A good prosecution is like rolling out a good tube of toothpaste," says Mitchell Epner, a former federal prosecutor turned criminal defense lawyer at New York firm Rottenberg Lipman Rich. "You get every bit out," he told AFP.

Asset in Russia investigation?

In the US justice system, those who cooperate can substantially reduce their sentence. Cohen is already facing four to five years behind bars. Epner said serving up substantial dirt could reduce that to as little as probation.

"I think the larger question is does he (Cohen) somehow pivot," says Diane Marie Amann, law professor at the University of Georgia, and become part of the probe into Russian interference in the 2016 election.

"That seems highly likely," she added.

Cohen's lawyer Lanny Davis told CBS News that his client had information about election tampering efforts during the 2016 campaign that would be "of interest to the special counsel."

"Speaking publicly is a way to message to many different people what further damage Mr Cohen may wreak against the president and his associates," Amann told AFP when asked about Cohen's possible strategy going forward.

"It may change the political climate in certain ways."

Cohen's plea deal does not obligate him to cooperate, but neither does it preclude cooperation. "He did not have to implicate anyone else," said Lisa Kern Griffin, a law professor at Duke University.

"It certainly suggests a commitment to cooperate."

So why did he do it?

What else does he have?

Even if Cohen wanted to tough it out, hoping the president would eventually pardon him, going to trial would have likely cost millions, with no indication that the Trump Organization would have picked up the tab.

Cohen's relationship with his former boss steadily deteriorated.

Trump left the one-time personal injury lawyer for dust after moving to Washington. After news broke he was under federal investigation, the president washed his hands of Cohen, saying it had nothing to do with him.

No doubt that sounded like a betrayal to the ex-Trump Organization executive vice president, who may have been dreaming of a White House job himself.

In July, Cohen reportedly told investigators that the US president knew in advance of a June 2016 meeting in which Russians were expected to share dirt on his then-election rival Hillary Clinton, directly contracting Trump denials.

But does Cohen have evidence to back-up any claims against Trump? His credibility is shot to shreds, both as a felon and by a history of ducking, diving and lying repeatedly.

"The big question is what else does he have?" said Epner. "If the only thing he has to offer is his testimony it's not worth a lot."

FBI agents raided Cohen's New York offices in April, seizing reams of documents that the lawyer could potentially authenticate and shed light on.

For the moment, Cohen's sentencing date has been set for December 12. If that is pushed back, it will be a tell-tale sign that he is cooperating further.