Three thugs were put behind bars by witnesses who at first were too terrified to give evidence.
People who saw a man kicked and punched to the ground in Goodwood Way, Moulsecoomb, Brighton, were frightened of repercussions.
Police spent days talking to them and eventually persuaded them to make statements.
Detective Constable Linda Guyton coaxed them and obtained special court orders allowing them to give evidence behind screens to protect their identities.
The ringleader was jailed for three years and two juveniles were sent to a young offenders' institute.
Miss Guyton, 29, was rewarded for her efforts with divisional congratulations at a ceremony at Brighton police station on Friday.
She was commended by Chief Superintendent Paul Curtis, head of Brighton and Hove police, for her "professionalism and tenacity".
Miss Guyton, who is engaged and plans to marry Brighton PC Darren Lynch next year, said it was nice to receive recognition.
She said: "The public often only hear bad stuff about police but there is a lot of great work that goes unnoticed."
Miss Guyton received a second certificate for her work on Operation Alva after a 16-year-old Swedish student was sexually assaulted on Brighton beach.
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