The first report by police was in 1963. He was a suspect in the attempt of killing mobster Jean-Baptiste Andréani. In 1967, he was again the main suspect in the drive-by-killing of Marseille mob boss Antoine Guérini. After this murder, "Mad Jacky" crew and Tany Zampa crew share the underworld business of Marseille and its suburbs. These main activities were prostitution, drug and protection racket. But his partnership with Zampa did not long. They had a dispute over protection rights. In 1968, he became à trotting driver with his friend Alain Delon. In 1973, he was champion of France.
On 1st february 1977, Mad Jacky survived on attempt of Murder by Tany Zampa crew. Legend has it that one of the men said: "a swine like him isn't worth le coup de grâce, let him die like a dog". He shot seven times and doctors removed 23 bullets from his body and his right arms stayed paralysed. About that, the french newspaper Le Monde wrote : "Small matters, he learnt to shoot with the left". Mad Jacky's revenge 11 of Zampa's associate were shot down. Imbert was arrested as he allegedly prepared for another killing. No charges were brought against him he was released after 6 months. When he came out a truce had been declared
After this period, Jacques Imbert seemed to lead a quiet life between these different properties: Caribbean, Italy and France. In 1980s, he was also a PR for a discotheque "Bus Palladium", in Paris, owned by his friend Richard Erman, a Russian born businessman.
In 1993, in a interview with Le Nouvel Observateur magazine, Imbert said: "The cop always come to ask me about the job I didn't do. For the ones I did do, I never saw anyone".
He was a close friend of Francis "the Belgian" Vanverberghe, mob boss too. He was killed on september 2000.
The 16th june 2006, Mad Jacky was sentenced to four years for exorting money from Paris businessmen in the early 1990s. The recent conviction is the first blemish on a clean criminal record. Imbert's counsel intends to appeal the verdict.
The 2nd january 2008, in appeal, Imbert's is sentenced to two years for "only" exorting money from a discotheque owner, in Paris.