The best coverage I have seen on this topic comes from the Human Rights in India Blog, run by the Human Rights organization Ensaaf. Ensaaf has done some truly excellent work on the Delhi 1984 Pogroms. Here they compare the Nanavati Commission report to their own investigation of the subject:
The report fails in similar ways as the Misra Commission report. In its report, Twenty Years of Impunity: The November 1984 Pogroms of Sikhs in India, ENSAAF analyzes thousands of pages of previously unavailable affidavits, government records and arguments submitted to the 1985 Misra Commission, established to examine the Sikh Massacres in Delhi, Kanpur, and Bokaro. The report reveals the systematic and organized manner in which state institutions, such as the Delhi Police, and Congress (I) officials perpetrated mass murder in November 1984 and later justified the violence in inquiry proceedings.
… police officers not only passively observed the violence, but also actively participated in the attacks and made promises of impunity to assailants. Senior officers: ordered their subordinates to ignore attacks against Sikhs; ordered policemen to disarm Sikhs to increase their vulnerability to attack; systematically disabled and neutralized any officers who attempted to deviate from the norm of police inaction and instigation; released culprits; and manipulated police records in order to destroy the paper trail of the violence and protect criminals from the possibility of effective future prosecutions. At all times, the police and their superiors had sufficient force and knowledge to effectively counter the violence.
ENSAAF’s report further demonstrates the involvement of the Congress Party in organizing the massacres. Senior political leaders provided for details such as deployment of mobs, weapons and kerosene, as well as for the larger support and participation of the police. They conducted meetings the night before the onslaught of the massacres where they distributed weapons, money, voter and ration lists identifying Sikhs and their properties, and in inflammatory speeches, instructed attendees to kill Sikhs.