ORLANDO, Fla. (Reuters) - The federal trial for the widow of the gunman who killed 49 people at a gay nightclub in Orlando, Florida, began on Thursday with the selection of jurors, who will decide whether she aided her husband in one of the deadliest U.S. mass shootings.

Noor Salman, wife of Omar Mateen, is the only person charged in the June 2016 attack on the Pulse nightclub and faces up to life in prison if convicted. Mateen, 29, died in an exchange of gunfire with police at the club.

Salman was at home with the couple’s then 3-year-old son during the shooting rampage. Prosecutors said she knew of her husband’s plans to launch an attack and did nothing to stop it.

Some protesters gathered outside the Orlando courthouse Thursday held posters encouraging a guilty verdict and calling for the death penalty. The trial could take as long as a month, court officers said.

Inside the courtroom, the owner of the Pulse nightclub, Barbara Poma, watched some of the initial proceedings.

U.S. District Judge Paul Byron questioned 10 potential jurors and dismissed four of them. The selection process resumes on Friday.

Although Salman initially denied the accusations, she later told federal investigators she knew that her husband was watching recruitment videos for Islamic State in Iraq and that he had purchased an assault rifle and examined three possible attack locations, they said in court documents.

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“The defendant aided and abetted her husband in this mass-murder and repeatedly lied to law enforcement,” they said in a court filing.

Defense lawyers contend the U.S. government could not show any direct links between Mateen and Islamic State before the attack and has provided no evidence that Salman aided her husband.

“It was Mateen, not Noor, who decided to attack the Pulse Night Club, Mateen who chose to drive to the club, Mateen who purchased the weapon and ammunition, and Mateen who alone carried out the attack,” they said in court filings.

Salman, 31, was indicted on two charges: obstruction of justice for alleged false statements to federal investigators, and aiding and abetting Mateen in his attempt to provide material support to a terrorist organization.

Mateen opened fire shortly after the last call for drinks on the club’s popular Latin night.

Holding hostages during his standoff with police, he claimed allegiance to a leader of the Islamic State militant group before being fatally shot.