Updated

Jurors in the trial of a Florida teen accused of killing two British tourists watched the teen mumble his way through an interview with police detectives and insist that he hadn't left his home the evening of the April 2011 murders.

Shawn Tyson, 17, is charged with two counts of first-degree murder. Defense attorneys have said there was no evidence tying him to the crime and that witnesses testifying against him were not credible.

Authorities say Tyson shot and killed British tourists James Kouzaris, 24, and James Cooper, 25, last April.

Attorneys selected a jury of nine women and five men Wednesday, and opening statements began Thursday morning. By mid-afternoon, prosecutors had already called eight witnesses, including several crime scene technicians who recounted taking photos of the young men's bodies and finding .22 caliber shells buried in the dirt near the crime scene.

Jurors sat grim-faced as the photos -- which depicted the men splayed on the grass of a housing project -- were shown.

Late Thursday afternoon, the jurors watched Tyson's videotaped interview from April 2011 with Sarasota Detective John Todd. Tyson repeatedly told Todd that he hadn't left his home the night of the slayings, but Todd and another detective didn't believe the teen. Todd urged Tyson to talk about who he was with that night and said that Todd's friends were all going to testify against him.

"You'd better harden up. You're in the big leagues now," said Todd. "Are you going to take the rap for this all by yourself?"

Todd explained to the jury that all of the witnesses in the case were close friends with Tyson. He added that three witnesses, including two neighbors, picked Tyson out of a lineup -- and said that the teen's lip quivered and tears came to his eyes when the detective explained that he could perform ballistics tests on a bullet found in Tyson's room and the bullets used in the killings.

Tyson is being held at the Sarasota County Jail without bail. If convicted, he faces life in prison -- because he is 17, he cannot face the death penalty.

The two men were dining and drinking in downtown Sarasota with Cooper's parents the night of April 15. The entire party was staying at a Longboat Key beach condo; Cooper's parents went back to the condo in a car and urged the two young men to take a cab back home.

The pair went to two bars and left on foot after several drinks. Shortly before 3 a.m., they ended up in a crime-ridden neighborhood more than a mile from downtown Sarasota. It's unclear why the men ended up in the area. Witnesses said they saw Cooper and Kouzaris walking shirtless and stumbling through the neighborhood -- and that they were being followed by two black men, one with a red bandanna around part of his face.

Prosecutor Ed Brodsky said Tyson told a friend that the men were lost and that he then tried to rob them. The tourists told Tyson they didn't have any money and pleaded for their lives. Both men were found with their pants down around their thighs; Det. Todd said he had once worked on a robbery-homicide where the victim's pants were partially pulled down.

Brodsky said Tyson told his friend: "Since you ain't got no money, then I have something for your a--."

The tourists' bodies were found shirtless on the street. Both men still had their wallets and did in fact have money; Cooper also had a cellphone and camera in his pants pocket. Authorities later found that Kouzaris' blood alcohol level was 0.243 and Cooper's was 0.214 -- well past Florida's legal limit for intoxication, which is 0.08.

Prosecutors say they will call an expert who found Tyson's DNA on one of the victims' clothing.

Defense attorney Carolyn Schlemmer said during her opening statement that there is nothing to tie Tyson to the shootings -- no murder weapon was ever recovered. She added that many of the people slated to testify against Tyson were either pressured by authorities, made deals with authorities in exchange for information on Tyson, or were unreliable drug users and convicted felons. Other witnesses lied to law enforcement, Schlemmer said.

"No witnesses will testify that they saw Mr. Tyson shoot Mr. Cooper and Mr. Kouzaris," Schlemmer told the jury. "Keep an open mind."

Tyson is the only person charged in the slayings.

The trial will continue on Friday with the continuation of testimony by Det. Todd.