The journalists appeared as character witnesses in the trial that started on 10 January. In court at the end of January, Nemmouche insisted again that he was not behind the attack that killed four people.
"I have absolutely no doubt about the fact that Mehdi Nemmouche who is present here was my jailer and torturer in Syria under the name of Abu Omar," said Nicolas Henin, one of four journalists who was kidnapped in June 2013 and held by the Islamic state armed group in northern Syria until April 2014.
Didier Francois, another of the hostages, also testified. He said he "had no doubt" Nemmouche was the jailer, and that Nemmouche had hit him with "around 40 blows of a truncheon", among other abuses.
Investigators say Nemmouche launched the attack shortly after returning from Syria, where he had allegedly fought on for jihadist groups.
Nemmouche's lawyers have called the prosecution’s use of the journalists’ testimony a “stunt” and a "trial within a trial" because their kidnapping is the subject of separate legal proceedings in France.
Nemouche claims innocense
At the end of January, Nemmouche told the court that he was innocent.
"I reiterate that I am not the museum killer, I condemn all acts of intimidation and call on everyone to let this trial take place in complete serenity," he said.
That same day, the two daughters of the Israeli couple, Miriam and Emmanuel Riva, who were killed in the attack, took the stand and described a devoted mother and unassuming father.
"We have to manage on our own even if we receive help from the family," Ayalet Riva, 19, said.
The trial is due to last until the end of February or early March.