Police have carried out detailed searches in the seaside town

Veronica Wilson, whose husband Alistair was shot in the head on the doorstep of their Nairn home, is being helped by a specialist family liaison officer.

Northern Constabulary have described the situation as "delicate".

Officers are said to be gently coaxing as much information as they can from the mother-of-two.

There are no plans at present for Mrs Wilson to make a public appeal, but the police have said that that could be an option in the future.

Officers have said they are not yet in a position to issue a photofit image of Mr Wilson's attacker.

On Wednesday, Detective Chief Inspector Peter MacPhee renewed his appeal to anyone with information about the killing in the Highland town on Sunday evening.

'Information mountain'

Police are sifting through a "mountain of information" which has been gathered as part of the investigation.

Cordons placed on roads following the shooting have now been removed, except for those around Crescent Road where the murder took place.

Officers are searching for a blue or green envelope which was handed to the victim moments before he was murdered.

Alistair Wilson, pictured on a family outing on the day he was murdered

It is understood Mr Wilson took the envelope from the gunman and left the doorway to speak to his wife.

Police have refused to disclose details of the conversation between the couple, but when Mr Wilson returned to the door he was shot at point blank range with what is thought to have been a small automatic handgun.

The killer ran from Crescent Road towards the links area of Nairn.

The envelope, which is not thought to have been opened, has not been recovered.

Detectives have vowed to pick apart Mr Wilson's life to establish a motive for his murder but have ruled out mistaken identity as the killer asked for him by name.

Mr Wilson's employers, the Bank of Scotland, said they could not comment on reports that he had recently handed in his notice to leave his business management post.

The gunman is described as being aged 35-40, stocky, clean shaven and wearing a baseball hat and blouson jacket.