The Central Bureau of Investigation (CBI) on Wednesday registered an FIR in connection with the death of 27-year-old Sreejeev, who died in police custody in May 2014.
Sreejeev's brother Sreejith has been staging an indefinite protest in front of the Secretariat seeking justice for his kin.
Sreejith has been demanding a CBI inquiry into his brother's death.
Sreejiv, died in a Thiruvananthapuram hospital, two days after he was taken into custody on charges of theft.
The police claimed that he committed suicide after being taken into custody by consuming poison.
Sreejiv's brother alleged that the police took his brother to its custody the day before a woman he was believed to be in a relationship with was getting married.
The victim's brother said that the police arrested his brother at the behest of the woman's relative, who was a policeman.