The British tourists who were gunned down in 2011 in Florida pleaded with their killer to spare them before he shot them dead, a court has heard.

Defendant Shawn Tyson, who was 16 at the time of the shooting, allegedly told a friend that he killed James Kouzaris and James Cooper after a failed robbery as they drunkenly walked through a housing project in Sarasota.

Latrece Washington, 18, said that Tyson told her that he shot the two tourists as they cried for their life.

"He said 'Well since you ain't got no money I got something for your ass,'" Washington recalled Tyson saying on the day after the killings.

Tyson told Washington that the men begged for their lives.

"One said, 'Please let me go home, I'm lost,'" she said. "He shot one of them in the side and one of them fell instantly and the other one was crying for his life. He shot him."

Kouzaris and Cooper died in April 2011. They were found shirtless with their trousers round their thighs, the court heard.