Pulse nightclub trial for Noor Salman begins: What to know about the Orlando shooter's widow

At one point, it was the deadliest mass shooting in modern U.S. history. Now, two years after 49 people were massacred inside a crowded nightclub in Orlando, the wife of the gunman responsible is on trial -- and families of the victims are looking for justice.

Omar Mateen opened fire with a Sig Saur semi-automatic rifle on June 12, 2016, killing dozens of people before he was fatally shot hours later by police. The trial of his widow, Noor Salman, will be the only criminal prosecution for the incident.

Testimony began this week in a trial that's expected to last at least three weeks. Salman faces up to life in prison if convicted. Here's what you need to know.

What is she being accused of?

Salman has pleaded not guilty to charges of aiding and abetting Mateen's allegiance to the Islamic State. She's also being charged with obstruction of justice, as FBI agents say she lied to them during questioning hours after the attack.

Assistant U.S. Attorney James Mandolfo says Salman gave conflicting statements to FBI agents. In one conversation with authorities, before they informed her of any details of the attack, she said, "My husband is safe with guns."

"No one ever told her about guns," Mandolfo said.

FBI agents interviewed Salmon three times after the attack. They said she was aware Mateen was planning to do something and that texts to her husband prove it.

"She knew he was going to conduct the attack," federal prosecutor Roger Handberg told a judge during a hearing in Oakland on Jan. 17, 2017.

One text recovered from Salmon’s phone reads, “If ur mom calls say nimo invited you out and noor wants to stay home.” Another reads, “She asked where you were xoxo. Love you.”

“Nimo,” or Nemo, is the name of one of Mateen’s friends, whom defense attorneys said Mateen often used to cover his tracks when he went out to cheat on his wife.

She shopped with her husband at Walmart the night before the attack when he bought five containers of ammunition, a source close to the investigation previously told Fox News.

A law enforcement source also told Fox she had driven her husband to Pulse nightclub at least once before the deadly shooting.

What is her defense?

The family and Salmon’s lawyers deny she had anything to do with Mateen’s plot.

In a November 2016 interview with The New York Times, Salman apologized for her husband's act and claimed she was unaware of his plan.

"I don't condone what he has done," she told the newspaper. "I am very sorry for what has happened. He has hurt a lot of people."

From various court documents, it is expected that the defense will say Salman was abused by her husband and feared for her life. Her attorneys also claim she wasn't given proper Miranda warnings, which tell suspects they have a right to remain silent and have an attorney present, before she made statements.

“I knew when he left the house he was going to Orlando to attack the Pulse Night Club,” Salman confirmed in a signed statement written by an FBI agent, according to documents obtained by the Orlando Sentinel.

Defense attorney Linda Moreno argues this confession was coerced and, therefore, should not be admissible in court.

"Noor Salman denied any knowledge of Omar Mateen's plans for hours," Moreno says, claiming agents told Salman that she could go to jail and not see her child.

What about her family?

FBI agents arrested Salman in January 2017 inside her California home, where she had been living with her young son, whom she shared with Mateen. 

The now 5-year-old boy, who lives with his maternal grandmother in California, has since learned about his father's act and hasn't had any contact with Mateen's side of the family, Susan Clary, spokeswoman for Salman’s family, told the Orlando Sentinel.

Salman reportedly calls the boy daily.

"They talk about what he learned in his kindergarten class that day and what his favorite toys are," according to the Florida newspaper.

What do we know about her trial so far?

U.S. District Judge Paul G. Byron, federal prosecutors and defense attorneys picked 12 jury members and six alternates on March 12.

Opening statements started in federal court on March 14 in downtown Orlando.

On the first day of the trial, jurors listened to a witness who hid under a dead body for three hours as shots were fired and an Orlando police detective who choked up on the stand. They also watched a video taken during the shooting by a survivor inside the club.

Jurors watched graphic videos of the massacre the next day. Salman shielded her face as the videos and images were displayed on screen, The Orlando Sentinel reports.

One video showed Mateen opening fire — shooting people already lying motionless on the dance floor. He then walked toward the restroom where he began targeting people hiding in the bathroom stalls.

Fox News' Phil Keating and The Associated Press contributed to this report.