Dear Sanjeev Kumar, the difference is already explained. Anyway, I would try to examplify it. If A is arrested for murder, police generally ask for police custody with a view to have clues of evidence and for recovery of weapons. When he is given in police custody, he remains in custody of police, i.e. in police lock up. Police custody can not be given beyond 15 days except where there is special provision to grant PC for more than 15 days. Police has unfettered powers to interrogate the accused in police custody in a lawful manner. Whereas in judicial custody, the accused technically remains in the custody of the magistrate. He can be kept in jail or other place of safety. Police can not interrogate the accused without permission of the magistrate if the accused is in judicial custody.