A famed Harvard legal scholar is raising concerns about the Justice Department's ability to responsibly handle some documents seized Monday from Trump lawyer Michael Cohen's offices.

Among the scooped-up papers, and lurking on phones and hard drives, is likely to be a cache of material that's covered by attorney-client privilege.

Prosecutors are not permitted access to those files, and the DOJ's standard practice is to set up a 'taint team' – a group of agents and lawyers not connected to the Cohen case or the special counsel probe into all things Russia – to decide what they can see.

But 'taint teams don't work,' Alan Dershowitz told DailyMail.com on Tuesday, because seizing the material in the first place was a violation of Cohen's constitutional rights – even if it's never used in court.

Dershowitz was at the White House on Tuesday afternoon in advance of a dinner appointment with the president, according to two officials.

Harvard Law School professor Alan Dershowitz said Tuesday that the Justice Department violated the rights of Donald Trump's lawyer Michael Cohen when the FBI seized his files on Monday, because of constitutional protections against unreasonable searches and guaranteeing the assistance of legal counsel

President Donald Trump invited Dershowitz to dinner on Tuesday at the White House, according to two sources there

Cohen is reportedly under investigation for allegedly making illegal campaign contributions to Trump in 2016 by giving the future president's former mistress hush money in order to help him win the White House, and for bank fraud related to his withdrawal of the payoff funds from his home equity line of credit

He said it's 'rare' for federal law enforcement to serve a no-knock search warrant on an attorney in a case as high-profile as the one now swirling around the White House.

But the investigative firewalls between FBI strike teams and prosecutors are 'not so uncommon,' UCLA Law School professor Harry Litman told DailyMail.com.

He said such teams are assembled 'several times a year' at the federal level, citing the 1993 civil rights trial of four Los Angeles police officers who were caught on camera physically attacking Rodney King, an African-American taxi driver.

UCLA Law School professor Harry Litman, no fan of Dershowitz, says 'taint teams' work well and there's 'absolutely no cheating' because the stakes are so high

Although the officers were acquitted in a California courtroom, the federal government won civil rights convictions against two of them.

But the Justice Department prosecutors in the second case weren't permitted to see anything related to the earlier criminal trial, Litman explained.

As a practical matter, he insisted, taint teams do their jobs well.

'I've experienced it,' he said 'There's absolutely no cheating, certainly at the federal level. The consequences are too severe.'

Litman called the Justice Department 'ultra-hyper-vigilant, even paranoid, about this precise issue.'

But for Dershowitz, who helped win a murder acquittal for O.J. Simpson and succeeded in overturning the attempted murder conviction of Claus von Bülow, the constitutional issues are more important than the DOJ's trustworthiness – and bigger than the presidency.

Dershowitz said Monday night in a Fox News Channel interview that it had been 'a very dangerous day today for lawyer-client relations.'

The concept of assembling a taint team, he said, revolves around the Fifth Amendment, which protects Americans from being forced to incriminate themselves.

So when the team sifts through Cohen's documents, hard drives and memory sticks, it will be searching for protected material that should be kept private.

But the Fourth Amendment prohibits 'unreasonable' searches and seizures by the government – a description that could apply to scooping up communications between a lawyer and his client, except in extreme circumstances.

And the Sixth Amendment guarantees Americans the right to 'the assistance of counsel' for courtroom defense, meaning no government can interfere with that relationship.

Dershowitz told DailyMail.com that 'if the government improperly seizes private or privileged material, the violation has already occurred, even if the government never uses them.'

'Remember who comprises the firewall and taint teams,' he explained, quoting in an email from what he said was a forthcoming column. It's 'other FBI agents, prosecutors and government officials who have no right under the Fourth and Sixth Amendments, even to see private or confidential materials, regardless whether it is ever used against a defendant.'

Ultimately, Dershowitz's beef may be with whichever federal judge green-lighted the DOJ's request for a search warrant covering the places where Cohen lives and works.

It's likely that the agency convinced the jurist that Cohen had documents showing evidence of a crime. But even so, the Harvard professor said, those documents could have been privately subpoenaed.

He compared Monday's document dragnet to government surveillance of a confession heard by a priest, a patient's discussion with her doctor, or a husband and wife talking about their sex life.

'The government simply has no right to this material,' he said.

Washington, D.C. criminal defense lawyer Barry Pollack told the Associated Press on Tuesday that it is 'extremely rare' for authorities to conduct searches in lawyers' offices.

Such a search warrant is a measure of last resort because of problems posed by the attorney-client privilege, according to the Justice Department's manual for federal prosecutors.

'Only if they have considered other means for obtaining the evidence they are seeking and have decided that other means are not going to be effective,' said Pollack, a former president of the National Association of Criminal Defense Lawyers.

After prosecutors decided they needed a warrant, they still had to get authorization from the top federal prosecutor in New York or a high-ranking Justice Department official. Prosecutors also had to confer with the department's criminal division, according to the rules.

Still, Dershowitz said Monday night in a Fox News Channel interview that it had been 'a very dangerous day today for lawyer-client relations.'

'If this were Hillary Clinton [having her lawyer's office raided], the ACLU would be on every TV station in America jumping up and down,' he protested.

'The deafening silence of the ACLU and civil libertarians about the intrusion into the lawyer-client confidentiality is really appalling.'