A self-confessed 19-year-old cannabis dealer has denied providing the gun which killed a 22-year-old man on a Luton estate.
Richard Long, of Houghton Regis, was shot through the head after being lured to the Lewsey Farm estate on 1 September, Luton Crown Court heard.
Simeon Johnson, 18, and the 19-year-old man, who can only be referred to as "M", both from Luton, deny murder.
M told the court he did not supply the gun or suggest robbing Mr Long.
M said his co-defendant Mr Johnson had lied to the jury in the account he had given.
Mr Johnson said it was M who told him to rob Mr Long and provided a gun, which he thought was unloaded.
Prosecutor Miranda Moore, QC, earlier told the jury the Crown's case was that it was never intended to provide the cannabis, but the plan was to rob Mr Long of the cash at gunpoint on the Lewsey Farm estate.
The prosecution said that although Mr Johnson was the gunman, the murder was a joint enterprise.
M admitted to the court he had been dealing cannabis for about a year-and-a-half.
He said Mr Johnson asked him at the end of August if he could provide a kilo of skunk, and he made some calls and said he could.
Arrangements were made to hand over the drugs, but M then wanted to watch Mr Johnson complete the deal, he told the court.
He said he climbed on a flat roof at St Dominic's Square but could not see Mr Johnson.
He went to look for him and saw him in a park area, with a man on the ground and heard gunfire.
"I was surprised and confused and ran off," he told the court.
"I did not know he had a weapon, and I did not supply him with a hand gun. There was no plan to rob him.
"I supplied the cannabis but robbing a customer would be bad for my business."
The case continues.