According to a detective in charge of investigating another murder of which Silcott was later convicted, police thought he was 'capable - either through himself or his friends - of suppressing evidence from witnesses', David Calvert-Smith, for the prosecution, said at the Old Bailey.
The officer - Detective Chief Superintendent Eric Brown - had led the inquiry into the murder of boxer Anthony Smith, 23, for which Silcott was jailed for life.
Mr Brown has given evidence for the defence in the trial of senior detectives accused of framing Silcott for the murder of PC Blakelock in 1985.
Superintendent Graham Melvin and Detective Inspector Maxwell Dingle deny conspiring to pervert the course of justice in the Broadwater Farm case. Supt Melvin also denies perjury.
Mr Brown said a young model had to be given police protection before she agreed to testify at Silcott's trial for the Smith murder. She was among those who had seen Silcott stab the boxer at a party, according to the detective.
'The principal witnesses in the room when the knife blows were struck were terrified. They were worried about attending court. Several received threatening phone calls,' he said.
The model had made a statement implicating Silcott. 'She was taken bodily from her place of work by four or five young black males and held. She was threatened that she would not be able to model again because she wouldn't be so pretty,' Mr Brown said.
He said Silcott denied being at the party and refused to sign notes of interviews he had with police.
The jury heard statement evidence yesterday from 14 witnesses whose identities were not revealed as they remain 'in fear', according to Richard Ferguson QC, for Det Insp Dingle.
The witnesses implicated Silcott in PC Blakelock's murder.
Police officers deputed to investigate PC Blakelock's murder were subjected to enormous pressure, Mr Calvert-Smith said.
Nicholas Purnell QC, defence counsel for Supt Melvin, 52, said there was no evidence to convict two senior detectives of fabricating evidence against Silcott.
The trial continues today.