In 1999, 43-year-old David Swain, the owner of Ocean
State Scuba in Jamestown, RI, and his 46-year-old wife
of nearly seven years, Shelley Tyre, chartered a sailboat
in the British Virgin Islands with friends Christian and
Bernice Thwaites and their son. The last day they were to
dive, they moored off Cooper’s Island to dive two tugboat
wrecks.
The couples had agreed that two adults would remain
  on the boat to watch the Thwaites’ boy, so Tyre and Swain
  went into the water. Swain returned to the boat alone 35
  minutes later, saying he was chilled. Christian Thwaites
  dropped into the water for his dive.  
Moments later Thwaites spotted one of Shelley Tyre’s
  yellow swim fins and looked for Tyre, figuring she would
  be grateful that he had found her fin. Instead, he found
  her lying on her back on the sandy bottom with her eyes
  and mouth open. Thwaites took Tyre to the surface,
  where he tried to perform CPR. Swain, who had been
  an emergency medical technician, helped lift his wife
  aboard, but did not try to resuscitate her. She was dead.  
James Philip Brown, who runs Aquaventure in Tortola,
  thought the death was suspicious. Tyre and the Thwaites
  had visited his shop to rent gear and discuss where to
  dive. A day after Tyre died, Brown dived the wrecks looking
  for something that might explain the death. Brown
  found one of Tyre’s fins embedded toe first in three inches
  of sand. He found her snorkel, sans mouthpiece, and
  her mask. On one side of the mask, the strap hung loose
  off its anchoring pin.  
Brown locked Tyre’s scuba gear in his office to await inspection by Tortola police. Two days later, Swain told
him that he could get rid of the equipment, give it to a
local diver or use it in the rental business. Brown refused.
Swain fretted that the medical examiner was taking a long
time to do an autopsy and asked if he knew anyone who
might “expedite the process.” Swain said that “the medical
examiner might not know about diving accidents,”
and he wanted to talk to him before the autopsy. Swain’s
remarks seemed irregular to Brown, enough for him to
approach Tortola police. But zno charges were brought.
  
    | 
 David Swain | 
Shelley Tyre’s parents asked Swain
  for an explanation of the death, but
  did not find him forthcoming. As
  more information came to light, and
  Swain continued to stonewall, they
  brought a wrongful death suit against
  him, which was heard over nine days
  in February 2006.  
A violent struggle
During the trial, Bill Oliver, a mechanical engineer
  who designs diving equipment and is product manager
  for Sherwood, presented videos of tests he conducted. He
  showed how Shelley Tyre’s fin would have simply sunk,
  heel first, under normal conditions, and how the strap
  of her mask could have pulled free if it had been yanked
  from behind. When Brown found Tyre’s fin, the heel
  strap was still fastened tight. Oliver testified that only a
  strong “external force” could have pulled the fin off.  
Dr. Thomas Neuman, a diving medicine specialist reviewed Tyre’s medical records, and said the five- foot,
one-inch woman weighed 120 pounds and was in good
health. She had logged at least 352 dives, and had no
reason to panic. Her tank was two-thirds full when it was
found and the dive site was a “benign” sand location.
The chief medical examiner of Miami/Dade County,
  Bruce Hyma, testified that evidence suggested a “violent
  struggle with another individual.” The pin holding one
  side of the mask strap in place was missing, indicating it
  had probably been ripped from the mask frame. Hyma, a
  diver for 36 years, said no medical condition would have
  interrupted Tyre’s normal breathing. With her experience
  she could have effectuated a self-rescue if she had
  the opportunity. “Her air supply was shut off,” he said,
  and he called it a “homicidal drowning.”  
Underwater forensic investigator Craig Jenni concluded
  that Swain had attacked his wife in 80 feet of
  water. Had Tyre encountered an emergency other than
  an attack, she would have dropped her weight belt to the
  surface as fast as possible. But Tyre was found with her
  weight belt still on. Her primary and octopus regulatory
  were working perfectly.  
Based on air still in Tyre’s tank when it was found,
  Jenni determined Tyre was underwater for about eight
  minutes before she stopped breathing. Divers normally
  swim about one foot per second while underwater, an
  important calculation considering what Swain said during his deposition: after a five-minute descent to the wrecks
together, he set off alone and made one revolution
around one of the sunken boats.
After considering the size of the wreck and Swain’s
  own mapping of his swim, Jenni figured it would have
  taken Swain about three more minutes to get back to
  where he had left Tyre. “At that precise time, Shelley
  was no longer breathing,” said Jenni, and Swain was in
  her vicinity. Even if she were already unconscious, Swain
  would have had to see her, Jenni said. But he came up
  alone. “The only conclusion,” said Jenni, “is David Swain
  attacked Shelley Tyre.”  
After the fact  
Keith Royle, a Tortola dive operator, responded to
  the Mayday call. When he got to the sailboat, he jumped
  aboard and offered to perform CPR, but was told it
  wouldn’t be necessary because Tyre was dead. He thought
  it unusual since he was taught “you do CPR until someone
  more qualified takes over.”  
Three hours after Tyre’s death, Swain gave a written
  statement to the Tortola police, saying his wife had swam
  off and left him by the wrecks. When he could not see
  her, he went looking for her. However, in depositions
  taken in 2003 and 2004, Swain said they dived together to
  the tugboats. Swain said it was common for them to split
  up — she counted fish and he took photographs. But, he then contradicted his statement to the police, saying he
swam around one of the wrecks before moving toward a
reef in shallower water. At some point, he said, he looked
back and saw Tyre, the last time he saw her alive.
When asked where was the dive computer he wore
  that day, which would have registered how long he was
  under the water and what depths he reached, Swain said.
  “I haven’t a clue.” He said he also could not remember
  where the photographs were that he took during the dive.
  Had he drawn any conclusions, asked Olenn, about how
  his wife died? “Nope,” said Swain.  
Swain’s testimony was on videotape. Swain did not testify
  on his behalf and chose not to be represented by his
  own counsel during the trial.  
Sex and Money  
Why would a dive shop owner murder his wife and
  dive buddy? Before the death, Mary Grace Basler testified
  that, she had rebuffed Swain’s advances, telling him
  she wasn’t interested because he was married, though he
  overnighted at her home once. Two weeks after Tyre died,
  Basler met Swain at a restaurant and in two months they
  were lovers, she said.  
While a prenuptial agreement prevented Swain from
  receiving anything from Tyre if they divorced, after the
  death Swain collected $570,000 from life insurance policies
  and Tyre’s investments. By February 2003, he was in
  debt from taking extensive trips to the Caribbean and
  other cities. He currently faces debts of $189,000.  
Swain chose to defend himself outside the courthouse.
  He said, “This is a tragic accident that is a personal matter
  between me and the Tyres” — his former in-laws. “I didn’t do it. . . . I feel for the Tyres. . . They have the pain to deal
with. I have pain to deal with too. But the thought that
we are going to work out this pain by going through this
is absurd . . . This issue of money . . . is not something I
want to be a part of.”
Tyre’s lawyer said it was not about money, “it’s about
  justice . . .Tortola authorities won’t do anything, and
  Rhode Island authorities can’t, and so it’s up to [the jury]
  to see that justice gets done.”  
The Verdict  
During closing arguments, the jury heard Tyre’s attorney
  tell how he believed Swain had killed his wife. Using
  a videotaped demonstration filmed underwater where
  one diver attacks another, he described how Swain had
  climbed onto Shelley Tyre’s tank, ripped off her face
  mask, shut off her air supply, and held her down on the
  sandy bottom.  
The eight member jury found Swain guilty and
  awarded Tyre’s parents $3,534,943 for compensatory and
  punitive damages. The standard of proof for a civil jury
  is whether “the “preponderance of evidence” leads them
  to believe that the alleged crime occurred. Jury foreman
  Robert Capello said the jurors were not convinced the
  attack happened as outlined, but “other than human
  intervention, how else could she have died? And who else
  was in the vicinity when it happened other than Swain.”  
After the verdict, Swain said, “I would welcome a criminal
  trial.” At least then “all evidence gets evaluated” and
  not just pieces. Swain is considering an appeal and has
  sued Shelley Tyre’s parents for defamation.  
From reports by Tom Moody, Providence Journal