Gardai are sifting through hundreds of hours of footage and hope to have images of the men early this week.

Sherlock was shot at pointblank range with a shotgun after he stopped a stolen Nissan Almera in rush-hour traffic on Ossory Road, Ballybough last Tuesday. The men escaped in a white van parked in a nearby housing estate and are being sought by a team of 70 detectives.

The life of the officer was probably saved by his motorcycle leathers and he has been released from hospital. The father of two is going through photo-fits of known armed robbers to see if he can identify the men who shot him.

The Sunday Tribune understands a list comprising over two dozen north Dublin criminals has been compiled and the alibis and movements of each individual on it are being investigated.

Detectives say it is likely the two men were on their way to carry out a robbery on a post office and not an assassination. Sources say it is their "gut instinct" that the men were probably "oldschool" criminals with experience of armed robberies.

They carried a sawn-off shotgun which is not favoured by younger criminals who use semi-automatic pistols because they are more reliable.

Gardai are also investigating whether a white van used by the gunmen to escape could have been one of the raider's personal vehicles. It is highly unusual that the van hasn't been recovered yet and it would have been expected that the vehicle would have already been recovered burnt-out.

Lists of everybody who owns vans in Dublin are being scrutinised in the hope of providing a breakthrough in the investigation.

Stories suggesting the garda might have been lured to be shot have also been dismissed. At least six garda cars were searching for the raider's car after its owner spotted it four months after it was taken from his house and dialled 999.