Mohammad Shahabuddin, who was sentenced to life in prison on Tuesday, has 52 criminal cases registered against him.
The Rashtriya Janata Dal's Lok Sabha member was awarded a life sentence in a case involving the kidnapping of a Communist Party of India-Marxist Leninist worker eight years ago.
His criminal career began in 1985 with a case registered against him in connection with a kidnapping at Siwan town police station.
According to police records, the criminal cases registered against Shahabuddin include murder, attempt to murder, kidnapping, extortion, offences under the Arms Act and Wildlife Protection Act.
He has been accused of links with Pakistan's notorious Inter Services Intelligence agency and fugitive gangster Dawood Ibrahim. Then Bihar Director General of Police D P Ojha alleged that Shahabuddin had links with the ISI. Ojha also accused the MP of links with the terrorist organisation, Lashkar-e-Tayiba.
It was the first time he had ever been convicted in a case.
He has been acquitted in 18 cases, including in two cases last week by the special court currently operating out of Siwan jail.
Shahabuddin is being tried in 29 other cases in different courts including the special court in Siwan jail. Four cases await a chargesheet.
He was first elected an independent member of Bihar's legislative assembly from Siwan's Ziradei seat in 1990, a constituency that includes the birthplace of India's first President Rajendra Prasad. Five years later then Bihar chief minister Lalu Prasad Yadav gave him a Janata Dal ticket to contest the assembly election. He easily retained the seat.
A year later, in 1996, Lalu Yadav asked him to contest the Siwan Lok Sabha seat. Shahabuddin has since won the seat four times in a row.