A former Scotland Yard detective has criticised the Police Service of Northern Ireland's (PSNI) investigation into the murder of Jim Donegan.
John Devitt said he cannot understand why police had not interviewed people who work in the industrial complex from where Mr Donegan ran his business.
"Twelve weeks down the line, for individuals not to have been seen is very concerning," he said.
The PSNI said detectives had spoken to 155 witnesses and arrested four people.
All were released and no-one has been charged in relation to the murder.
Father-of-two Mr Donegan was shot at the wheel of his Porsche as he waited to collect his 13-year-old son from school on Glen Road in west Belfast on 4 December.
The gunman was seen on CCTV fleeing from the murder scene and wearing a yellow high-visibility jacket.
Mr Donegan ran a car sales business from an industrial complex at Drumbo, between Lisburn and Belfast.
Det Ch Supt Raymond Murray, the head of the PSNI's serious crime branch, said detectives had visited the premises "within hours" of Mr Donegan's murder.
'Waiting for police'
Some people working at the business park said the police had not called there to ask them if they had seen anything suspicious in the run-up to the killing.
"After he was shot we expected the police to come and we've been waiting ever since," said one worker.
"You would have expected them to have come by now and you would have expected them to come as close to the event when things might be still clear in your mind.
"If you were a cop would you not come and talk to the people who worked in the same yard as him?"
Another said: "No-one has been in to see us or anything - no cops.
"I actually seen Jim the day that he was killed.
"He was in the yard here, he came in a taxi and then he drove out later in his Porsche - he waved and said hello and that was it.
"That was about 10:30 in the morning on the day he died so that was about five hours before he was shot."
Mr Devitt, a former Met detective and policing expert, said some of those working in the other businesses in the park should have been asked by now if they had seen anything suspicious before the killing.
"Given the length of time from the murder, I am actually quite shocked that police have not been there," he said.
"I think [this] is a major issue and police have major questions to address.
"It tells me their priorities are not as they should be.
"The golden hours in any murder investigation is the first 24 hours, let alone the first hour of an investigation."
'Focused in west Belfast'
But the PSNI's Mr Murray defended his team's handling of the inquiry.
Detectives had "very quickly established that Mr Donegan does not appear to have been targeted from his business premises", he said.
"The main focus for the inquiry, both in terms of the actual shooting and the weeks leading up to it, are strongly focused in west Belfast and that has driven the direction of the enquiry," he added.
Press reports at the time of his murder linked Mr Donegan to the drugs trade - something his wife Laura has denied.
Mrs Donegan declined to do an interview.
The PSNI said its investigation into the "callous execution" of Mr Donegan was "progressing".
"A dissident republican element remains a main line of inquiry," it said.
Mr Murray added: "I would like to reassure Mr Donegan's grieving family that the police investigation will continue along the lines of intelligence and facts, which only the PSNI are fully sighted on."
Last week, the Police Ombudsman's Office announced that it had started an investigation into how the PSNI dealt with information about a potential threat to Mr Donegan received before his murder.
The ombudsman is investigating whether the information was properly processed.