Former Uttar Pradesh minister Raghuraj Pratap Singh alias Raja Bhaiyya has agreed to undergo a lie detector test as part of the CBI probe into the murder of Kunda DySP Zia-ul-Haq. Haq was shot dead on March 2 at Balipur in Kunda area of Pratapgarh district where he was investigating the death of village head Nanhe Yadav. Bhaiyya appeared before a special CBI court in LucAknow on Tuesday and gave his consent to undergo a polygraph test.