A Manhattan grand jury could decide whether to indict Donald J. Trump in the days ahead, potentially touching off a sequence of events that could include the unprecedented sight of a former president in handcuffs.

But much about what comes next remains unclear. Prosecutors have signaled that an indictment is likely, but it is not a certainty. Before Mr. Trump can be charged, the Manhattan district attorney, Alvin L. Bragg, must ask the grand jury that has been hearing evidence about the former president to vote on whether to charge him. A majority of jurors must agree to do so.

The timing of any potential indictment, arrest and arraignment is unknown, and likely to remain so after a vote is conducted.

The investigation, conducted by Mr. Bragg’s office, has been focused on Mr. Trump’s involvement in the payment of hush money to a porn star during the final days of the 2016 presidential campaign.

Here’s what we know and don’t know about the course of the investigation and what might happen.

When might Mr. Trump be indicted?

The special grand jury that has been hearing testimony meets three afternoons a week, on Mondays, Wednesdays and Thursdays. At least one more witness could be called before jurors are asked to vote, according to people familiar with the matter.

Once all the witnesses have testified, prosecutors must explain the criminal charges they are seeking to the jury of 23 Manhattan residents before asking them to vote. A simple majority is all that is required to hand up an indictment.

How soon could Mr. Trump be arrested?

If Mr. Trump is indicted, prosecutors would most likely work with his legal team to arrange his surrender in Manhattan. Within several days of his indictment, Mr. Trump, who lives at his Mar-a-Lago resort in Florida, would travel to the city and turn himself in at the district attorney’s office in Lower Manhattan. Hours later, he would be arraigned in a courtroom in the same building.

Any indictment of Mr. Trump would almost certainly be sealed, and the charges would be kept secret from the public after the grand jurors vote. The unsealing of the indictment — and a public announcement of the charges against him — would coincide with his surrender and arraignment.

However, there is some chance that Mr. Trump does not surrender — there have been differing reports on that possibility — which could kick off a more complex scenario.

Might Mr. Trump avoid indictment entirely?

Mr. Trump’s lawyers have met with prosecutors in hopes of warding off criminal charges, and while it is unlikely, there is a faint possibility that Mr. Bragg will opt not to seek an indictment (or that he will seek one and grand jurors will vote to reject it).

But prosecutors have broad discretion during grand jury proceedings and the defense has almost no role. Every available signal has suggested that an indictment is imminent.

What might the charges be?

While it is clear that Manhattan prosecutors have been investigating the role Mr. Trump played in a hush-money payment to the porn star, Stormy Daniels, the specific criminal charges prosecutors could seek are unknown — and will probably remain so even after he is indicted.

People with knowledge of the matter have suggested the charges would stem from the falsification of business records that recorded reimbursements to Michael Cohen — Mr. Trump’s former lawyer and fixer and the prosecution’s star witness — as legal fees. Such a charge, combined with a second crime involving illegal campaign contributions, could rise to a low-level felony.

How do you arrest a former president?

Some of the routine steps that follow any felony arrest in New York would apply to the former president as they would to anyone else: He would be photographed and fingerprinted, and read a standard Miranda warning offering him the right to remain silent.

But because of Mr. Trump’s status as a former president — and his ’round-the-clock Secret Service detail — prosecutors are likely to make some accommodations. He could be held in an interview room instead of a cell; the investigators who process his arrest may forgo handcuffs.

Law enforcement agencies around New York have also had discussions about how to prepare for the prospect of protests, which Mr. Trump called for explicitly on his social media site, Truth Social, over the weekend. A protest in Manhattan on Monday evening was sparsely attended.

Will Mr. Trump be held in jail?

Because of the nature of the potential charges against Mr. Trump, the law does not allow prosecutors to seek to have him held on bail. And as a leading presidential candidate, he is far from a flight risk.

Mr. Trump will almost certainly be released shortly after he is arraigned.

What happens after that?

Once Mr. Trump has been charged, the case against him will probably be mired in protracted litigation. Should the matter eventually make it to trial, it could conceivably play out in the run-up to the 2024 presidential election — with Mr. Trump, the defendant, in the thick of his campaign.

Chelsia Rose Marcius contributed reporting.