Shawn Tyson is charged with two counts of first degree murder after allegedly trying rob, then shooting dead, James Kouzaris, 24, and James Cooper, 25, in Sarasota.
The friends were holidaying with Mr Cooper's parents and had been out in central Sarasota, when they drunkenly walked into a public housing estate known as The Courts in the early hours of April 16.
Tyson declined to give evidence in his defence and today the defence rested its case. The jury is expected to retire later today after closing arguments from both the defence and the prosecution.
Prosecutor Ed Brodsky told the jury today that the case was about "seized opportunities".
"For James Cooper and James Kouzaris they had seized an opportunity to travel abroad, to travel to Sarasota, Florida, for a three-week vacation and they were here with James Cooper's parents and their friend.
"What the evidence showed you during this week and last week is that this defendant right here, Shawn Tyson, seized upon the opportunity to rob and kill two men that had left the Gator Club in the early morning hours of April 16, 2011.
"And who inexplicably had wandered away from the Gator Club, were intoxicated, were on foot, and found themselves.... in the Old Projects in Newtown.
"In the aftermath of the homicides of James Cooper and James Kouzaris, the Sarasota Police Department would launch an investigation that would find them interviewing dozens of witnesses, forensically scouring the scene for evidence, searching cellular phone records, listening to jail calls and sending off evidence for scientific analysis.
"The culmination of the investigation that was conducted by the Sarasota Police Department based on the testimony that you heard during this trial, based on the evidence that you heard during this trial, would lead to only one inescapable conclusion.
"And that was that Shawn Tyson was responsible for the deaths of James Kouzaris and James Cooper."
Mr Brodsky said: "This investigation would not be easy, homicide investigations are not easy.
"They are not going to come wrapped to the Sarasota Police Department with a silver bow."
He said it would be "nice" if the victims were found in someone's house, if there was a murder weapon, and if the defendant confessed, but added: "That's not reality, and that's not what happened."
Mr Brodsky said Tyson's friend Latrece Washington had said he told her he had killed the men.
She told the court Tyson told her one of the tourists cried for his life as his friend was shot, then was gunned down himself.
She said Tyson claimed to have told the victims that since they did not have any money, he had "something for your ass".
Miss Washington told her mother, and reported it to police the following day, Mr Brodsky said.
He said she had told how Tyson said he shot one man in the side, which medical examinations later confirmed, but she could only have known such details if Tyson had confessed to her.
Although Tyson, then 16, told police he was home all night, he was spotted by neighbours Wanda Farrior and Roger Shavers running to his house just after the gunshots, and climbing into his window.
In his closing argument, Mr Brodsky asked why Tyson would have lied to detectives about being at home.
"Why? Because you are responsible, that's why," he said.
He said Tyson's friend Jermaine Bane heard Tyson saying on the phone just before the shootings that he had seen two "crackers" (white people) walking through the park.
"If you're at home, how are you in a position to see that?" Mr Brodsky asked.
The prosecutor said phone records also showed Tyson was "up and talking" around the time of the murders, not sleeping.
He said various people had given evidence about seeing Tyson with a red bandana round his neck.
"It is certainly reasonable to conclude that on that early morning hour of April 16 the item that he would habitually carry he would use to shield him during this robbery and homicide."
The families of Mr Kouzaris, from Northampton, and Mr Cooper, from Hampton Lucy, Warwick, are not in court for the trial, but two of their close friends are.
Mr Brodsky said Tyson told detectives that two 0.22 calibre bullets found in his bedroom were for a gun he had found in a ditch.
But the prosecutor said friends testified that Tyson owned a 0.22 calibre gun and often carried it.
Marvin Gaines said Tyson gave him shell casings and a gun to bury.
Jessica Cunningham told the court that on April 7, Tyson pulled a gun on her and her niece and threatened: "I'll kill both of you bitches."
Tyson was arrested after the incident and was released on April 15 - the day before the murders.
He was arrested after the shootings and on April 17 made a call to his half-brother from prison in which he said police had found "the bullets", which were the only thing that would "f*** him up".
Mr Brodsky said: "Your vocabulary and the words that you use mean everything and he said 'the bullets'."
He added: "In this case the phone records, the jail call, the admissions that he made to numerous individuals would conclusively prove to you that Shawn Tyson is responsible for the deaths of these two men.
"The evidence will show you that Shawn Tyson wasn't home, that he had been up talking before and after the murders, that he would readily admit his involvement to a number of his friends who were brave enough to come into this courtroom and recount for you what had occurred."
Mr Brodsky said the men were found with their trousers pulled down - a common tactic in robberies, according to police.
DNA that could be Tyson's was found on Mr Cooper's jeans - statistics showed 80 out of every 100 men could be excluded from that DNA profile, but Tyson was among 20 to be included.
Mr Brodsky said that by carrying a gun and firing it several times at Mr Kouzaris and Mr Cooper, Tyson could have had no clearer "premeditated" intent than to kill them.
He said the teenager exercised his constitutional right to a trial, but told the jury: "He has had his trial, it's time to now hold him accountable for the deaths of James Cooper and James Kouzaris."
The defence has argued that many witnesses gave evidence only in return for deals or benefits.
In her closing argument today, defence lawyer Carolyn Schlemmer quoted comments made by detectives and prosecution lawyers to various witnesses in the case.
"That is what this case is all about - threats, deals, benefits, moving services, getting-out-of-jail-free cards, rewards, offers for cash, bargains, elimination of prison sentences totally, and lies."
She said Detective John Todd, from the Sarasota police department, told the court that many people did not originally tell the truth to police.
Miss Schlemmer said the prosecution had to prove the case beyond a reasonable doubt.
"A not-guilty verdict in no way is going to lessen what happened to Mr Kouzaris and Mr Cooper that day."
She told the jury that several witnesses in the case had been convicted of crimes.
She said Bane had told three different versions of the descripton by Tyson of "two crackers", telling the jury: "How hard is it for him to just say what he said? He cannot keep his lies straight."
Miss Schlemmer said 0.22 calibre bullets were extremely common, and there was no firm link between Tyson and the murders.
Of the phone call Tyson made to his half-brother from jail, she said: "In a year, is that the best they can do?"
She said Tyson was not around when the gun was cleaned, or the casings dug up.
"Don't let the state try to tell you that a 16-year-old boy with a 9th grade education is some kind of criminal mastermind."
She said DNA evidence only showed Tyson could not be excluded from the profile found on Mr Cooper's jeans.
"Which version of any of these stories from these people do you want to believe?"
PA
