CCTV shows the moments before a Saudi student was fatally stabbed in the neck by a stranger as he sat with friends outside his university accommodation.
Mohammed Algasim, 20, died of a single stab wound across his jugular vein after an altercation on the evening of 1 August last year.
Chas Corrigan, 22, who denies murder and is on trial at Cambridge Crown Court, is seen in CCTV approaching the student and his friends as they sit on a low wall.
Abdullah Bin Shuail, one of Mr Algasim's fellow students, said he heard the pair exchange words but could not make out what they were saying.
Nicholas Hearn, prosecuting, previously told the court the pair had never met before.
Corrigan then walked towards the train station before Mr Algasim said something to him.
Mr Bin Shuail could only make out one word, "centre", Mr Hearn said.
"When Mr Algasim said this, the defendant turned and started to come back towards them," he continued.
The prosecutor said the defendant said "what did you say, what did you say?" in a "very angry and aggressive way".
He said Mr Bin Shuail "saw the defendant punch Mr Algasim hard to the left side of his neck" and "then saw that the defendant was holding a large knife in his right hand".
The stab wound, which also cut across his carotid artery, caused "massive bleeding", Mr Hearn said.
Jane Osborne KC, opening the defence case, said Corrigan "had a kitchen knife - tucked into his waistband rather than in the pocket".
"He will tell you he had no intention of using that knife," she said.
"He had it with him so if he was attacked, as he had been in the past, he could frighten off any attacker.
"He wanted to prevent himself being a victim of violence again."
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She said Corrigan will say "in the incident Mr Algasim was standing in front of him, he thought Mr Algasim was acting aggressively".
"He thought he (Corrigan) was imminently going to be attacked so he produced the knife," she said.
"Having produced the knife Mr Corrigan had no intention of using it to cause Mr Algasim any harm.
"He intended to wave it between them.
"He will say he had no idea he had made contact with Mr Algasim with the knife."
The trial, estimated to last around two weeks, continues.
(c) Sky News 2026: CCTV shows the moments before Saudi Cambridge student Mohammed Algasim is fatally stabbed
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