[1] He was elected to the Lok Sabha, the lower house of the Parliament of India from Outer Delhi as a member of the Indian National Congress but resigned from the primary membership of the party after he was convicted and sentenced to life imprisonment for his role in the murder and involvement in the 1984 anti-Sikh riots.
[4] In 1991, he was re-elected to the Lok Sabha, and then again in 2004 when he won by the largest number of votes ever in India, 855,543, representing Indian National Congress in outer Delhi.
In 1984, a fact-finding team jointly organized by People's Union for Democratic Rights (PUDR) and the People's Union for Civil Liberties (PUCL) concluded that attacks on members of the Sikh community in the 1984 anti-Sikh riots were not from spontaneous outrage over the assassination of Indian prime minister Indira Gandhi, but rather the result of deliberate planning by important politicians of the Indian National Congress party.
The investigators found that the member of parliament who was most commonly named by Sikh riot survivors for being responsible for the attacks in the Delhi locality of Sultanpuri was Sajjan Kumar.
[6] In 2010, as a result of the CBI investigation, Kumar was tried for murder, dacoity, mischief to cause damage to property, promoting enmity between different communities, criminal conspiracy, and other provisions of the Indian Penal Code.
[15] It later rejected another interim bail plea on 4 September and said he did not need to be admitted to a hospital,[16] but stated it will hear his appeal after the courts resume their regular functioning which was affected due to the COVID-19 pandemic.