The accused has been identified as Rahul, police said, adding that he had confessed to killing Chuach Cue, the Burmese student, on June 3 with two others, including a juvenile.
Cue, a student of BA (1st year) in Delhi University, was hospitalised in unconscious condition with a stab injury and succumbed to the injuries during the treatment, police said.
On June 6, Rahul was found taking smack after which he was brought to the police station and was interrogated.
Efforts were on to nab the other accused, they said.