Naba Kishore Das was shot in the chest, allegedly by Gopal Das, n January 29.
Senior BJP leader Prakash Mishra claimed attempts were being made to prove that suspended ASI Gopal Das, the alleged murderer of Odisha Health Minister Naba Kishore Das, was mentally unstable so that punishment for him was relaxed.
Mr Mishra, a former director general of police of the state, also questioned the timing of declaring the health minister dead after being shot at in Brajarajnagar in Jharsuguda district on January 29.
"The Crime Branch investigation is not on the right track. Attempts are being made to relax the punishment for Gopal Das. The manner in which the probe is being carried out indicates that efforts are being made to declare him mentally unstable," he told reporters on Thursday.
According to the post-mortem report published in the media, the bullet hit the minister's left side of the chest and normally a person dies within five minutes under such circumstances, Mishra said.
"Then, how was he airlifted to Bhubaneswar and operated upon at a private hospital?" he questioned.
Also, the empty shell of the bullet used in the killing is yet to be recovered, he said.
"Gopal Das may claim in the court that he had not fired the bullet as the shell was never recovered. He may also question how the minister survived for so long after being shot on the left side of the chest at 12.35 pm on January 29?" he said.
Mr Mishra said it was a criminal offence to conceal the exact time of death and demanded that those trying to do it be booked.
He demanded to know why the results of polygraph and Narco analysis tests of Gopal Das conducted in Gujarat were not made public.
Minister of State for Home Affairs, T K Behera, said investigation is on the right track and all efforts are being made to bring a conclusive end.