A teenager has been arrested over the fatal stabbing of 20-year-old Lewis Elwin in Tooting, south London, on 18 April.
The teenager was arrested on suspicion of murder on Monday. He was taken to a south London police station where he remains in custody.
Elwin, from the Wandsworth area, was last seen during the afternoon of Monday 18 April jogging along Penwortham Road where he collapsed.
Emergency services were called to the scene over reports of a stabbing.
Police officers found Elwin suffering from stab injuries, and a short while later he was pronounced dead at the scene.
A post-mortem examination at St George's Hospital Mortuary on Tuesday 19 April revealed Elwin's cause of death to be a stab wound through his back.
The murder investigation is being led by Scotland Yard's homicide and major crime command.
Detective Chief Inspector Diane Tudway who is leading the investigation said: "This attack took place in broad daylight in a residential street and there would have been witnesses to the incident, or the events immediately before or after the incident."
Police officers are urging witnesses and anyone with information about the incident to come forward.