Kavan Brissett, aged 21, was knifed in his chest in an alleyway off Langsett Walk, near Upperthorpe, last August.
CRIME: Fears over number of children recruited into gangs – with over 50 criminal groups operating in South Yorkshire He underwent emergency surgery as medics battled to save his life but he died in hospital four days after the attack.
Detectives investigating the stabbing want to speak to 30-year-old Ahmed Farrah, who they believe could hold vital information about the stabbing.
Farrah, who has links to Broomhall and is also known as Reggie, is said to know he is wanted for questioning but is actively evading arrest.
An 18-year-old man was arrested on suspicion of attempted murder and three boys - two aged 17 and one aged 16 - were arrested on suspicion of conspiracy to rob following the murder but were not charged.
A Crimestoppers reward of £5,000 is available for information leading to Farrah’s arrest but anyone who spots him should call 999 immediately.