File pic: Controversial UP minister Raja Bhaiya
A court today rejected the CBI's report closing its probe into the case and ordered the agency to reinvestigate the killing.
The CBI had said there was no evidence against Raja Bhaiya, or Raghuraj Pratap Singh, who is Food and Civil Supplies Minister in the state's Akhilesh Yadav government.
Raja Bhaiya resigned in March, days after his name came up in the murder of Deputy Superintendent of Police Zia Ul Haq.
Mr Haq was killed on March 2 in Pratapgarh district, where he had gone to investigate a village headman's murder. An angry mob reportedly cornered him, and eight policemen who were with him allegedly abandoned him. Three bullets were fired - one killed Mr Haque; the other two killed headman Nanhe Yadav's brother.
Mr Haq's wife blamed the killing on Raja Bhaiya, who represents Pratapgarh as an independent legislator.
The CBI, however, gave him a clean chit after hours of interrogation and a lie-detector test.
He was taken back into the state cabinet, with Samajwadi party Chief Mulayam Singh Yadav making a rare appearance at his swearing in ceremony.
Raja Bhaiya faces eight criminal cases, including those of attempt to murder, robbery and dacoity. He had been jailed for nearly a year in 2007, when the Mayawati-led BSP was in power.