The US Attorney’s office appears to have the smoking gun that may be the first of a long line of prosecutions resulting from the financial crash of last year.

Sources tell The Post the most damning evidence against Bear Stearns’ hedge fund managers Ralph Cioffi and Matthew Tannin appears in an e-mail message from Tannin to Cioffi, which states: “The entire subprime market is toast, there is simply no way for us to make money — ever.”

By contrast, the two hedgers held an investor conference call soon after and told investors “We’re comfortable with exactly where we are.”

“There’s no basis for thinking this is one big disaster,” Tannin said on another call in April.

In a trial that will be watched by many investors, the feds are scheduled to begin jury selection on Tuesday in Brooklyn federal court.

If Uncle Sam wins its case against the pair, the feds could start seeking criminal charges against other financial pros swept up in the crisis. If convicted, the defendants face between 20 to 40 years in prison.

Among the theatrics at last Thursday’s pretrial conference before US District Court Judge Frederic Block included:

* During the hearing about the admissibility of Tannin’s Gmail online diary, the lawyers were at each other’s throats, hurling accusations at one another and cutting each other off.

* Judge Block got caught up in the fray, at one point telling prosecutors James McGovern and Patrick Sinclair, “I’m gradually losing my patience with you” and then adopting a mocking, whiny tone later when addressing the prosecutors’ concerns.

* Judge Block also told the defense lawyer she was “getting a little hyperactive.”

* Judge Block admonished the prosecutors saying, “If you don’t have enough evidence in these 500 exhibits and 38 witnesses against these people then maybe you shouldn’t be successful.”

Bankers are wearily eyeing the case as a litmus test for the government’s ability to go after other Wall Streeters who may have been less than forthright about the extent of losses tied to the meltdown.

“Whenever the government wins a prosecution, they will feel encouraged to look for the same or similar cases,” said Mark Zauderer, a corporate attorney. Winning shows them “juries are receptive” to such cases, he said.

But it’s not just jury sympathy that could prod similar charges. Also at issue is the government’s ability to criminally convict on what can be a tricky legal issue.

“They [the feds] have to show that Cioffi and Tannin intended to lie,” said Ross Intelisano, a New York securities attorney. Proving intent, as it’s known, is tough, which is why this kind of case is typically tried civilly and not criminally, Intelisano said.

The defense is expected to argue that the duo was unable to predict the magnitude of the meltdown, just like most financial pros.

Bolstering the government’s case is a string of e-mails, including private e-mails between Cioffi’s Gmail account and Tannin’s wife’s e-mail account, showing the two fretting over their investments and even discussing shuttering the funds.

Cioffi is also accused of moving $2 million out of one of the shaky funds into a safer fund — something he failed to disclose to investors.

Another Judge Block decision going against the prosecution last week was that the prosecution could not use as evidence Cioffi’s lavish lifestyle.

Prosecutors were hoping to allege that Cioffi was motivated to cover up the losses by a desire to keep up his lavish lifestyle, which included multi-million dollar homes in Long Island, Manhattan, Vermont and New Jersey, as well as several vintage Ferrari’s and country club memberships.

“Good luck with a Brooklyn jury deciding your fate knowing you’re running around in a $1 million Ferrari,” said Intelisano.

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