The jury found 45-year-old Griffin guilty despite his claim that he had no recall of the incident because he had blacked out in their room at the five-star Le Bristol hotel near the Champs Elysees in May 2009.
His wealthy girlfriend, Kinga Wolf, 36, died of massive internal bleeding and her skull, jaw and larynx were smashed. More than 100 marks were found on her body.
Griffin claimed the couple had argued over dinner after she refused him the anti-depression pills to which he had become addicted.
He said she then pressured him for sex, but he was in no state and refused.
“She was very upset,” Griffin told the court in evidence on Tuesday.
He left the restaurant before her intending to “get my car keys and leave”, but she made it back to their hotel room before him.
“When I walked into the room and heard her voice, I went into a total blank, nothing,” he told the court.
Griffin said he had woken the next morning to find the room in an “awful” state and tried to clear up the mess.
He claimed he had not found his girlfriend’s body, between two mattresses, until the afternoon.
Presiding judge had expressed surprise at his evidence, asking why it took so long for him to think of his girlfriend, who owned a company that supplied supermarkets with tomatoes.
Giving its verdict, the court said Griffin was responsible for his actions, pointing to his “attempts to delay the discovery of the body”, and to his contradictory account of the events.
The prosecution had called for a 30-year sentence.
Griffin was arrested in England in June 2009 and extradited to France in May 2011. He was later released due to a neurological condition but had to wear a security tag.
He ran tanning salons and gadget shops in northwest England before being declared bankrupt in 2006- AFP