A man accused of murdering Graham and Carole Fisher during a raid on their garage told a court he had nothing to do with the killings.
The Fishers were both shot three times before being bludgeoned
Lee Firkins, and his brother, Robert, from Weston-Super-Mare, deny killing the couple at their bungalow near Wadebridge, Cornwall, in November 2003.
Mr Firkins told Exeter Crown Court they were in the area to see relatives and "to buy some puff [cannabis]".
But he admitted he would fire a gun in a robbery "if need be".
Lee Firkins, 31 and Robert Firkins, 33, deny killing Mr Fisher, 60, and his 53-year-old wife were killed in a robbery at their garage in November 2003.
When Lee Firkins began giving evidence, he was asked by defence counsel James Wood QC whether he had been at the garage on 5 November, and he said he had not.
He denied being involved in the murders or entering the bungalow.
The prosecutor alleged the Firkins brothers - originally from Dagenham, Essex - had planned to rob the Fishers but on the night what actually happened appeared to be "robbery gone wrong when things got out of hand".
The court heard that on 29 December 2003, police dug up a package buried on the beach at Sand Bay, Weston-super-Mare, containing a sawn-off 12-bore double-barrelled and a sawn-off .410 shotgun which were linked to the defendants by fingerprints and DNA evidence.
Lee Firkins said the weapons were acquired in London after 5 November to protect him and his family from threats made to them which had forced them to move to Somerset.
The jury had been told the brothers have already pleaded guilty to other serious offences committed at the end of 2003.
On 18 December, the brothers robbed the B&Q hardware store in Taunton, Somerset.
The following day, Lee Firkins was involved in an armed robbery at a petrol station at Fraddon, Cornwall, in which he fired a double-barrelled shotgun at the wall.
Cross-examining Lee Firkins, prosecutor William Boyce questioned him about the Fraddon robbery, when he was armed with a sawn-off shotgun.
"Were you going to fire it?" asked counsel. "If need be," said Firkins.
"If the person you are robbing is too slow to give you the money it would need to be fired?" asked counsel. "OK, yes," said Mr Firkins.
Asked whether he had ever fired a shotgun before 19 December, Firkins replied: "Not to my knowledge, no."
The trial continues.