Luchman Singh (58), a BSP activist and former gram pradhan died in a police station at the Rampur Maniharan town in Saharanpur district on Saturday, police said.
Singh was taken into police custody in connection with an inquiry regarding the murder of his nephew, they said.
A murder case has been registered under various sections of IPC and Dalit Act against SHO Vegpal Singh, sub Inspector S K Tyagi, Constables Dharmendra and Gudheg, SSP Saharanpur D K Choudhary said, adding all the four accused have been suspended.