A witness called the police after listening to one of the young men on trial for a Northampton teenager's murder "laughing and joking" just hours after the fatal knife fight.
The 20-year-old man told the Northampton Crown Court how the 17-year-old boy "seemed proud of whatever had happened" as he sat around a friend's flat just two hours after Liam Hunt was stabbed in the neck.
But the 20-year-old called the police the next day when he realised he could have spent the night hearing a first-hand account of the stabbing.
Yesterday (March 15), he told the jury at Northampton Crown Court: "I was worried for [the girl who owned the flat]. I told her she might be harbouring a criminal."
The court also heard how "three or four black lads" came to the flat and sat with the 17-year-old defendant, the witness and two girls who had witnessed the knife fight.
The 20-year-old witness said: "They were all laughing and joking and seemed proud of whatever had happened.
"I can't remember in particular what it was they seemed proud of."
The same 17-year-old defendant, who can't be named because of his age, is accused of kicking Liam Hunt in the face during the fight. Liam's blood was found on his shoe by firensic scientists.
During the night, the witness claims he heard an account of the attack that places one of the defendants, Lee Warren, 18, from Queen's Park, as standing near the fight shouting 'where's my shank'.
It contradicts other eyewitness' stories that another defendant, Aaron Joseph, 20, from London, repeatedly shouted "where's my shank" before stabbing Liam Hunt in the leg.
Jospeh's defence barrister, Mr Benjamin Aina, said: "[That night] the name Aaron Jospeh was never mentioned, is that correct?"
The witness said: "That's correct."
The defendants in the trial are expected the take the stand and give evidence within the next week.
The trial continues.