Police said the man, who is in his 60s had been arrested on suspicion of assisting an offender and taken to Wymondham Police Investigation Centre for questioning. He remains in custody.
Mr Lawal, 25, died after he was stabbed in Thetford shortly after 7pm on Thursday, October 3.
Police found people on the side of the A134 Brandon Road getting first aid to Mr Lawal, who was pronounced dead just before 8pm.
Four men had previously been arrested including two men aged 26 and 29 who have been released under investigation while a 17-year-old male has been bailed until 30 October 2019 while enquiries continue.
A fourth man, aged 48, arrested in connection with the incident on suspicion of possessing a bladed article and Class A drugs, has been released under investigation.
On Monday, David's father Albert Lawal paid tribute. He said: "All the family loved him and he was a quiet, friendly and hardworking young man. We were all very proud of him when he was awarded his degree in accountancy and finance."
Mr Lawal died from a single stab wound to the neck/upper chest area.
Roy Brame, councillor for Thetford, lives near the scene of the murder.
He said: "To me it was quite scary as it was 30 yards away from my house.
"It has been extremely quiet, it's very scary when it is on your doorstep though.
"Usually when something like this happens people can't stop talking about it but this has just been so quiet."
Investigations are continuing and Det Chief Insp Phillip Gray urged people with information to come forward.
He said: "I would like to reassure the public we have a team of detectives working through witness statements, as well as CCTV and forensic enquiries to establish the circumstances leading up to Mr Lawal's death.
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