What is an indictment? What it means for someone to be indicted by a grand jury and why Trump was charged

• An indictment is the formal notification that a grand jury has brought charges against a defendant. 
• A grand jury is convened in some criminal cases to decide whether prosecutors have enough evidence to bring a defendant to trial. 
• After the indictment is brought, the defendant is formally arraigned on criminal charges.

A Manhattan grand jury voted to indict former President Donald Trump on Thursday after hearing evidence for months about his alleged role in a hush-money payment to adult film actress Stormy Daniels.

With that vote, 76-year-old Trump became the first former US president ever to be indicted on criminal felony charges in American history.

So what does it mean to be indicted?

An indictment is a formal notice to a defendant that they have been charged with a crime, according to the US Department of Justice.

In the US, when prosecutors are trying to bring a felony case against a defendant — either on the state or federal level — they may present evidence to a grand jury instead of filing the charges themselves.

In order to be prosecuted on a felony charge in New York, where Trump was indicted, there has to first be an indictment, unless that right is waived by the defendant, Mark Bederow, a defense attorney and former prosecutor for the Manhattan district attorney's office, said.

Waiving that right would be somewhat uncommon, Bederow told Insider.

"An indictment is a finding by a grand jury that there is reasonable cause to believe the target committed a crime," he said. 

Before that happens, the grand jury — a secret panel — is convened and then presented with testimony from witnesses and documents collected during a criminal investigation.

After that, the grand jurors are allowed to ask questions. Prosecutors will tell them what charges are being sought and explain the circumstances around each one.

When that's done, the grand jury will deliberate and then vote on which — if any — charges they will indict.

In New York, where Trump was indicted, 16 out of an originally selected 23 grand jurors must be present for a voting quorum, according to the state grand juror's handbook.

From there, a majority of 12 grand jurors must find there is reasonable cause to believe the accused person committed a crime, a standard lower than proof beyond a reasonable doubt, which is necessary to find them guilty.

When the vote is cast, and the charging documents are filled out, the indictment is filed under seal.

Prosecutors will then alert lawyers for the defendant about the indictment and upcoming arraignment. 

Depending on the charges, potential flight risk, and danger to the public, the defendant will either be arrested and taken into custody, or allowed to surrender.

Lawyers for Trump said he will voluntarily surrender to the Manhattan District Attorney's office.

Why was Trump indicted?

The charges against Trump remain under seal, and the indictment is expected to be unsealed only when Trump is arraigned in Manhattan. That's expected to happen on Tuesday.

"Here Trump was not 'charged' first. He was indicted, then he will be arrested Tuesday and formally arraigned," Bederow said.

The indictment's specific contents have not yet been made public, as is common in state criminal cases. It's also unknown if the indictment charges codefendants or just Trump. 

Two sources told CNN that Trump faces more than 30 counts related to business fraud.