Jean-Baptiste Mugimba was born in 1956 in Mutura commune, Rwanda. He is a former employee of the National Bank of Rwanda. He is married and has three children.
Mugimba is believed to have been the secretary-general in the Coalition for the Defence of the Republic, a Hutu extremist party accused of planning and executing the genocide against the Tutsis in 1994. He allegedly participated in the planning, preparation and execution of the killing and seriously wounding of Tutsis in the communes of Nyamirambo and Nyarugenge, the secteurs Nyakabanda, Kimisagara, Biryogo and other parts of Kigali. He has furthermore been said to have spread the genocidal ideology and therefore to have incited the population to commit genocide.
On 8 April 1994, Mugimba reportedly hold a meeting on genocide planning at his home in Nyakabanda, on the outskirts of Kigali. During that meeting, he was allegedly involved in the drafting of lists of Tutsis living in Nyakabanda which were later given to the Interahamwe militias. He has furthermore been said to have decided which roadblocks needed to be erected, and to have requested weapons to distribute to Interahamwe militias. On that same day, he was reportedly also involved in the killing of a former Tutsi colleague.
Mugimba was reporteldy involved in numerous attacks on Tutsis in the commune of Nyarugenge, the secteurs of Nyamirambo, Kimisigara, Biryogo, Nyakabanda, and other parts of Kigali. He allegedly participated in an attack in which three girls were abducted and killed, and in an attack on the offices of the Red Cross in Nyakabanda in which many Tutsis were killed.
He fled to the Netherlands in 1999, where he was reunited with his family which was already living there.
On 23 January 2014, Mugimba was arrested at his home in Leusden pursuant to an arrest warrant issued by Rwanda on 22 November 2012.