A French court will give its verdict this week in the case of two women accused of trying to set off a car bomb near Notre Dame Cathedral, after a major trial set out to expose the key role of female jihadists in homegrown terrorism.

On the night of 3 September 2016, Inès Madani, 22, and Ornella Gilligmann, 32, parked a grey Peugeot 607 with no number plate on a narrow street in front of busy restaurants near the cathedral in central Paris.

The car was loaded with six gas canisters. Fuel was poured over it and a lit cigarette thrown in. The court heard that if it had exploded it would have caused a devastating firebomb and killed or injured at least 60 people in a nearby bar.

But the women had chosen diesel – much less flammable than petrol – and, despite several attempts, the car did not catch fire. The state prosecutor said that only this mistake avoided “carnage”.

A court sketch of Inès Madani, 22, who posed online as a male Isis fighter. Photograph: Benoît Peyrucq/AFP/Getty Images

In a three-week trial which has gripped France, lawyers told of the women’s difficult childhoods and backgrounds which included failure at school, sexual assault, drug use, family difficulties and pressure for being overweight.

Madani and Gilligmann both acknowledged roles in the failed Notre Dame car attack, but both accused each other of taking the lead and pushing them to reluctantly take part.

Much of the trial focused on Madani, 19 at the time of the attack, who posed on social networks under various male pseudonyms of Islamic State fighters in order to seduce women into online relationships and encourage women into terrorism. Pretending to be a man, she attracted several women into online courtships, in which they pledged themselves in marriage. Each time, Madani disguised her voice on the phone.

Posing as “Abou Soulayman”, a jihadist just back from Syria, Madani had approached Gilligmann through social networks and an online religious quiz. Gilligmann quickly entered into an “intense virtual relationship”.

A court sketch of Ornella Gilligmann, who entered an ‘intense virtual relationship’ with Madani. Photograph: Benoît Peyrucq/AFP via Getty Images

The court heard that Gilligmann, who had experienced difficult births with all of her three children and suffered postnatal depression, had exchanged more than 6,000 messages with “Abou Soulayman” in a short period of time, saying they communicated every hour and “fell asleep on the phone, woke on the phone”. Gilligmann said they “talked about marriage, the future, children” and she sent nude photos of herself.

The court heard that Madani had liked the attention of the women who fell in love with her fake male personas online. She said it filled an “emptiness”, telling the court: “I didn’t have much to do with my days.”

The court heard that Madani, the fourth of five daughters of a bus driver, had turned to both drugs and religious study after being sexually assaulted aged 17. A close female friend had left for Isis’ self-proclaimed “caliphate” in Syria and Madani’s father had warned the authorities his daughter was also susceptible to leave for jihad.

The court heard that Madani spent “80% of her time in her room, under the duvet, the blinds closed … on her computer or phone. She lived like a recluse.”

When Madani and Gilligmann finally met in a burger bar in the Paris suburbs a few weeks before the failed Notre Dame attack, Madani said she was the sister of “Abou Soulayman” who had come in his place. Later, in prison awaiting trial, Gilligmann was said to have continued to struggle to accept that Abou Soulayman had never existed.

The court psychiatrist who assessed the women said each had been radicalised before they came together and “each wanted to show the other they were the greatest jihadist”.

Thibault de Montbrial, a lawyer representing civil parties to the case, told the court the “social and economic excuses” should be set aside. He said Madani was “a major figure in jihadism in France and expert in manipulation”, and that Gilligmann had also been extremely radicalised “before meeting her virtual prince charming”. He said they had both belonged to a terrorist network.

The state prosecutor called the women “the face of female jihad”, saying they had sought to cause maximum death.

When the car bomb failed to ignite, the women fled. Gilligmann was arrested in the south of France. Madani, following the advice of her Isis handler, went to Boussy-Saint-Antoine, a small town south-east of Paris, where she joined other women who were said in court to have become radicalised.

Fearing they were being watched by police, Madani and the women she was with fled the flat armed with a kitchen knife. One woman attempted to stab a plainclothes officer and Madani was shot in the legs by police officers as she fled.

In total, five women were on trial accused of involvement in a terrorist group or terrorist activity. The court, made up of professional magistrates without a jury, was told that two of the women had suffered sexual assault or rape, others had experienced weight issues or an eating disorder. Many had had troubled relationships with their family.

Another woman and man were accused of failing to report a terrorist crime.

Rachid Kassim, an Isis fighter who was said in court documents to have coordinated the failed Notre Dame attack as well as other attacks in France from his base in Syria, was also on trial in absentia. He is believed to have been killed in Iraq, but without proof of his death he was tried.

A verdict is expected on Monday or Tuesday.