A Florida jury found a teenager guilty on Wednesday of gunning down two British tourists in the coastal town of Sarasota after they stumbled into a high-crime area in April 2011.

Jurors deliberated for about two hours before declaring Shawn Tyson, 17, guilty of two first-degree murder charges in the deaths of James Kouzaris, 24, and James Cooper, 25. The two visitors were out drinking in Sarasota when they got lost.

They were found shirtless, with their pants down, and shot to death in a housing project known for high crime, Assistant State Attorney Ed Brodsky said.

Tyson received two sentences of life in prison without the possibility parole for killing the men. He did not face the death penalty because of his young age.

Brodsky told jurors during closing arguments on Wednesday that all trails of the investigation led to Tyson, particularly the critical testimony of one of the teen's friends.

The friend said Tyson had told her he saw the drunk men and was going to rob them.

According to the friend's testimony, Tyson said the men told him they didn't have any money, and Tyson responded: Since you ain't got no money, I got something for your ass.

Tyson said he then shot one man on his side, causing him to fall instantly, and shot the other man until his gun ran out of bullets, according to the friend's account.

Defence attorney Carolyn Schlemmer argued that reasonable doubt remained in the case. She questioned the credibility of the witnesses, some of whom have criminal records.

Most of them told several versions of events and conflicting stories about what colour bandana Tyson wore or the gun he owned, Schlemmer said.

No witnesses said they saw Tyson shoot the two men, and the murder weapon was not found, the defence said.

The prosecution pointed to Tyson because he had a .22-caliber hand gun and bullets that matched the kind found in the bodies of the tourists, Schlemmer said.

But the defence attorney said those were extremely common bullets used in different types of guns, and there was nothing unique about the ones found lying on Tyson's bedroom floor during a search to tie him to the crime.

Tyson did not testify during the week-long trial.

(Editing by Cynthia Johnston and Todd Eastham)