PARIS — Four people go on trial on Monday on charges of conspiring to commit a terrorist act in connection with the murder of a Catholic priest inside a Normandy church in 2016.

Father Jacques Hamel was slain by two 19-year-old attackers as he celebrated Mass on a quiet summer weekday in the small Normandy town of Saint-Etienne-du-Rouvray.

The Islamic State group claimed responsibility for the attack, in which two nuns and an elderly couple were held hostage before the assailants slashed the priest’s throat and seriously wounded the other man. Another nun slipped away and raised the alarm, and police fatally shot both attackers as they left the church.

The four men going on trial are suspected of having helped or encouraged the attack.

Three were present at the Paris court on Monday.

The fourth, Rachid Kassim, a Frenchman who was a notorious Islamic State recruiter, is being tried in absentia: he is believed to have been killed in a drone strike in 2017 near the Iraqi city of Mosul. He is suspected of having used social media to encourage the attack.

Kassim had already received a life sentence in absentia three years ago for having ordered a failed attack in Paris, in which two women who pledged allegiance to the IS group blew up a car in 2016 near Notre Dame cathedral.

The three other suspects in the Catholic priest murder case each face 30 years in prison.

Jean-Philippe Steven Jean-Louis, 25, wanted to go to Syria and travelled to Istanbul with one of the attackers, Abdel-Malik Petitjean. He allegedly knew that Petitjean intended to commit an attack in France and is accused of having set up an online money collection site to help finance the project.

Investigators said Jean-Louis had spread IS group propaganda through a Telegram channel on which he encouraged extremist acts.

Farid Khelil, 36, is Petitjean’s cousin and is accused of having knowing about and supporting the attack.

Yassine Sebaihia, 27, was in contact with one of the dead attackers.

The 92-year-old parishioner who was wounded in the church during the attack is attending the trial.

His spouse, also held in hostage in the church, had told investigators the priest had been specifically targeted by attackers because “they directly moved toward him and put him on his knees.”

The verdict is scheduled to be rendered on March 11.