Lawyers in Donald Trump's historic criminal trial on Thursday selected 12 jurors who will assess his guilt or innocence over the coming weeks in a case stemming from a hush-money payment to a porn star.

Lawyers for the defence and the prosecution still must select alternate jurors for the trial, the first ever in which a former U.S. president is the defendant.

Earlier in the day, Justice Juan Merchan excused another juror after prosecutors said he may not have disclosed prior brushes with the law.

Trump's outsized public presence has created unique problems as lawyers worked to assemble a panel of 12 jurors and six alternates for the trial, which stems from a hush-money payment made to Stormy Daniels shortly before Trump was elected president in 2016.

Roughly half of the 196 prospective jurors screened so far in heavily Democratic Manhattan have been dismissed after saying they could not impartially assess his guilt or innocence.

Trump's criticism of witnesses, prosecutors, the judge and their relatives in this case and others has sparked concerns about harassment, prompting Merchan to impose a partial gag order.

Merchan dismissed the juror who said she felt intimidated after family, friends and colleagues had deduced that she had been selected for the trial.

"I don't believe at this point that I can be fair and unbiased, and let the outside influences not affect my decision-making in the courtroom," the juror said.

WATCH | The task of finding unbiased jurors for Trump's trial:

12 jurors selected for Trump hush-money trial — after a few hiccups

After a few hiccups, 12 jurors and one alternate have been selected for Donald Trump's hush-money trial. The former U.S. president is lashing out, calling the trial 'unfair' even after he was accused of violating a gag order.

Trump, the Republican presidential candidate in the Nov. 5 election, also faces criminal cases in Washington, D.C., Georgia and Florida, but the New York case is the only one certain to go to trial this year. Officials involved in those cases have reported receiving death threats and harassment after being criticized by Trump.

Trump has pleaded not guilty in all four cases and has said, without evidence, that they are part of a broad-ranging effort by allies of Democratic President Joe Biden to hobble his candidacy. A conviction would not bar him from taking office.

In New York, Trump is accused of covering up a $130,000 payment his former lawyer, Michael Cohen, made to porn star Daniels for her silence before the 2016 election about a sexual encounter she says they had a decade earlier.

Trump has pleaded not guilty to 34 counts of falsifying business records brought by Manhattan District Attorney Alvin Bragg and denies any such encounter with Daniels, whose real name is Stephanie Clifford.

WATCH | Former federal prosecutor on hush-money payments:

Why Trump prosecution is focusing on campaign finance violation, election interference

Former federal prosecutor Joseph Moreno explains why hush money payments weren't illegal, but the way they were concealed may have been.

Cohen pleaded guilty to campaign finance violations in 2018 and served prison time for making those payments, and Trump's lawyers are expected to attack his credibility as a witness.

"Some of the witnesses have what you might consider to be some baggage," prosecutor Joshua Steinglass told potential jurors, adding that several have publicly denied some of the alleged conduct they will hear about in this case.

Merchan has taken steps to shield jurors in the case from harassment, saying they will remain anonymous except to Trump, his lawyers and prosecutors. On Thursday, he said he would prohibit news outlets from reporting on aspects of potential jurors' employment.

Trump's willingness to criticize those involved in the case, combined with the widespread public interest in it, could put jurors' safety at risk, said Michigan State University law professor Barbara O'Brien.

"These are just people showing up doing their civic duty," she said. "They're not voluntarily injecting themselves into a public conversation."

Prosecutors say Trump has violated Merchan's gag order seven times since they flagged three potential violations on Monday, and have asked the judge to impose fines or other penalties.

On Thursday, prosecutor Christopher Conroy pointed to posts saying undercover liberal activists had been lying to the judge to try to get on the jury.

One of Trump's lawyers, Emil Bove, said those posts "do not establish any willful violations" of the gag order.