Karim Cheurfi was a deeply troubled, introverted and "psychologically fragile character" but appeared unlikely to get involved in Islamist extremism, according to his former lawyer.
Jean-Laurent Panier, who defended the suspected Champs-Elysée gunman in a theft trial, said he showed "no sign that he belonged to any movement, or of radicalisation".
Mr Panier added: "He was very solitary, someone who was particularly isolated. He lived with his mother and had contact with his father, and there was a family that tried to support him but felt powerless."
Cheurfi had a long criminal record and spent more than a decade in prison for attempted murder.
The lawyer painted a picture of a naive man, who took part in a theft and was "left to face the music" when his accomplices fled.
"I never got a sense that this was someone who would be radicalised," Mr Panier said.
A 39-year-old French national, Cheurfi had been under preliminary investigation for terrorism since March.
He had been questioned in February over threats to kill police officers but allowed to go free.
He was not on the police "S" watchlist of known terror suspects although he appeared on the counter-terrorist services' radar last December, according to 'Le Monde', slightly earlier than previously thought.
At the time, police were tipped off that he wanted to "kill police officers to avenge Muslims killed in Syria", said the newspaper citing security forces. He was also seeking weapons and a way of contacting an Isil contact in Iraq or Syria. A judicial inquiry was opened in Meaux but this was not terror-related.