Madi Mahaboubi, a 31-year-old father of two young children, is charged with killing Violet Price, 80, and disposing of her remains in woods around south west France.
The pair were both at a family barbecue in Eymet, a town hugely popular with the British, last Saturday before Ms Price was reported missing from her home in nearby Moustier, in the Dordogne.
But Mahaboubi led police to a wood around 15 miles away, close to the village of Tombeboeuf, where he lived with his wife and two young children.
Body parts were found "in two separate locations", said local prosecutor Pascal Prache, who revealed Mahaboubi was in 2005 sentenced to eight years in prison for manslaughter in the French overseas territory of Mayotte, near Madagascar.
Mahaboubi, who was born and brought up on the archipelago, had moved to the Dordogne on his release, in order to start a new life.
He settled in the village of Tombeboeuf, where he found work as an electrician and plumber servicing local properties, but had recently split up with his partner.
"The body parts of the victim were found just 400 metres from Mr Mahaboubi's house," said a near neighbour in Tombeboeuf, who asked not to be identified.
"His partner recently left with the children. They'd been having a lot of arguments."
Two cups of coffee - one half drunk - were found in Ms Price's home after she went missing.
Dozens of police supported by a helicopter and sniffer dogs had searched for the pensioner, who lived alone.
She had not been seen since she attended the barbecue with family members, including her son Paul.
It is thought Mahaboubi watched Ms Price leave the gathering alone in her car, and later went to her home.
Officers who later visited the house found the lights on, Ms Price's car parked in front of the property and no sign of any kind of struggle.
Mrs Price was originally from London, and moved permanently to France three years ago, to be closer to her son.
She and her late husband, Harry, bought the house in Moustier 15 years ago, originally as a holiday home, and to rent it out. Mr Price died last year.
The Dordogne, east of Bordeaux, is hugely popular with British expats and second home owners, who move there for the beautiful countryside and relatively cheap property prices.