The detention order was issued under the provisions of the Prevention of Terrorism Act, allowing investigators to detain and interrogate the suspect for an extended period.
The suspect was arrested in Delduwa, Ambalangoda, by a team of officers following intelligence received by police. He was taken into custody when officers arrived at a house where he had been staying while allegedly conducting surveillance in a nearby cinnamon estate.
Investigations have revealed that the suspect had been hiding in the cinnamon plantation during the daytime and returned to the house only at night to sleep in an apparent attempt to evade arrest.
Police said the suspect is believed to be the gunman who first opened fire on the lawyer using a T-56 assault rifle, fatally shooting him.
According to investigators, after carrying out the shooting, the gunman fled in the same vehicle used in the crime and got off in Kottawa. He then travelled by bus to Maharagama and later boarded another bus to Ambalangoda.
The suspect, a 46-year-old resident of Baddegama, is reported to have previously served in the Sri Lanka Army.
