After deliberations over two days, the 12-member jury announced on Thursday it had found Trump guilty on all 34 counts he faced. Unanimity was required for any verdict.

The verdict plunges the United States into unexplored territory ahead of the November 5 presidential election, when Trump, the Republican candidate, will try to win the White House back from Democratic President Joe Biden.

Trump, 77, has denied wrongdoing and was expected to appeal.

He faces a maximum sentence of four years in prison, though others convicted of that crime often receive shorter sentences, fines or probation. Incarceration would not prevent him from campaigning, or taking office if he were to win.

Opinion polls show Trump and Biden, 81, locked in a tight race, and Reuters/Ipsos polling has found that a guilty verdict could cost Trump some support from independent and Republican voters.

The jury found Trump guilty of falsifying business documents after sitting through a five-week trial that featured explicit testimony from porn star Stormy Daniels about a sexual encounter she says she had with Trump in 2006 while he was married to his current wife Melania. Trump denies ever having sex with Daniels.

Trump’s then-fixer Michael Cohen testified that Trump approved a $US130,000 ($A196,000) hush money payment to Daniels in the final weeks of the 2016 election, when he faced multiple accusations of sexual misbehaviour.

Cohen testified he handled the payment, and that Trump approved a plan to reimburse him through monthly payments disguised as legal work. Trump’s lawyers hammered Cohen’s credibility, highlighting his criminal record and imprisonment and his history of lying.

Falsifying business documents is normally a misdemeanour in New York, but prosecutors in Manhattan District Attorney Alvin Bragg’s office elevated it to a felony on grounds that Trump was concealing an illegal campaign contribution.

Trump complained that he could not get a fair trial in his heavily Democratic hometown.

The case was widely regarded as the least consequential of the four criminal prosecutions Trump faces. Jurors heard testimony of sex and lies that have been public since 2018, although the charges themselves rested on ledger accounts and other records of Cohen’s reimbursement.

It was known as the “zombie case” because Bragg brought it back to life after his predecessor opted not to bring charges.

This case was also likely to be the only one to go to trial before the election, as the others are delayed by procedural challenges.

If elected, Trump could shut down the two federal cases that accuse him of illegally trying to overturn his 2020 election loss and mishandling classified documents after leaving office in 2021. He would not have the power to stop a separate election-subversion case taking place in Georgia.

Trump has pleaded not guilty in all the cases, and has portrayed his various legal troubles as an effort by Biden’s Democratic allies to hurt him politically.