The 38-year-old man has already admitted to killing Maelys and faces life in prison.
ADVERTISEMENTA former French soldier has gone on trial over the kidnapping and murder of an eight-year-old girl in 2017.
Nordahl Lelandais has already admitted to killing Maëlys de Araujo and faces life in prison if convicted by the court in Grenoble.
The 38-year-old dog trainer is also facing charges of sexually abusing two children in their sleep.
The death of de Araujo in August 2017 sent shockwaves across France and the investigation led authorities to suspect Lelandais of other crimes.
The young girl's family were in attendance at the criminal court of Isère on Monday, carrying a picture of their daughter.
Eight-year-old Maëlys disappeared from a wedding in the French Alps on 26 August 2017 in the town of Pont-de-Beauvoisin.
After a massive search that drew nationwide attention, investigators identified a wedding guest as the main suspect.
Lelandais had not originally been invited but had contacted the groom one day before and subsequently came to the wedding reception. After providing cocaine to two guests, he invited Maëlys to see his dogs in his car, according to investigators. He later returned to the wedding after the girl was reported missing.
He was identified as a suspect within days and initially denied any involvement in the girl's disappearance despite mounting evidence.
Maëlys' body was discovered six months later after Lelandais admitted to killing her and a trace of her blood was found in his car.
Lelandais told investigators that Maëlys started crying in an “incomprehensible” way and that he punched her several times violently in the face, without intending to kill her.
The suspect told the Grenoble court he wanted to apologise, stating “I indeed took the life of Maëlys. I didn’t want to.”
Interrogations of Lelandais led police to investigate the disappearance of another soldier Arthur Noyer, who went missing in 2017 from a gay nightclub in another region of the Alps.
Lelandais acknowledged killing Noyer after a fight and was sentenced to 20 years in prison for the murder last year.
During sentencing, Lelandais admitted to prosecutors that he had a drug and alcohol problem and that he was sexually attracted to young girls.
The former army soldier is also accused of sexually abusing two cousins --aged 5 and 6 -- during a holiday in southern France in 2017.
Lelandais was also charged with sexually assaulting another 14-year-old cousin in the Ardennes and is suspected of other unsolved crimes.
A verdict in the trial over the murder of Maëlys de Araujo is expected on February 18, more than four years after her death.