Mark Duggan, 29, was shot dead by police on August 4 last year in Tottenham, north London.
He was killed moments after getting out of a taxi which had been stopped by armed police.
Officers have said Mr Duggan raised a handgun he was hiding in his jacket.
Today, a jury at London's Snaresbrook Crown Court heard that Mr Duggan was looking to sell cannabis and had sought the help of his friend, Kevin Hutchinson-Foster.
Hutchinson-Foster is on trial accused of supplying Mr Duggan with the gun he is alleged to have been wielding before he was shot.
Hutchinson-Foster, a cannabis user with convictions for possession of cocaine and heroin with intent to supply, said he regularly used cannabis but offered to get involved with Mr Duggan on a bigger deal.
The defendant said that in July last year he had a conversation with Mr Duggan and a friend called "Mo" about the deal.
Asked by his barrister, Stuart Denney, what the thrust of the conversation was, he said: "They knew somebody who was cultivating cannabis and wanted to know if I knew anybody who was interested in buying it.
"I said if they got me a sample I would give it to my dealer to see if he was interested."
Hutchinson-Foster, 30, of no fixed address, is charged with "selling or transferring a prohibited firearm" to Mr Duggan between July 28 and August 5 last year.
He denies passing the modified BBM Bruni Model 92 handgun to Mr Duggan, contrary to the Firearms Act 1968.
