Dateline: Unforgettable - Why did David Swain murder his wife Shelley Tyre? Details from the true crime episode, revisited

Oxygen's Dateline: Unforgettable re-examined the case against David Swain in the January 3, 2024, Episode 48 of Season 2, titled The Last Dive.

The show reviewed the tragic homicide of Swain’s wife, Shelley Tyre, who drowned when they were on a scuba diving trip in the British Virgin Islands in 1999. Swain was found guilty of her murder in 2009, but the conviction was reversed in 2011.

Dateline: Unforgettable re-examines the suspicious nature of the events surrounding the death of Shelley, putting together forensic evidence, personal histories, and court fights that left audiences and jurors baffled over the age-old question: was it a tragic diving accident or murder beneath paradise’s surface?

Since the moment David Swain called Shelley's family to inform them that she was dead, the investigation was marred by suspicion. Family and friends were in disbelief, and shortly thereafter, rumors began to emerge: David was not only experiencing marital stresses and financial difficulties, but he allegedly had eyes on another woman.

With every new discovery, the theory that Shelley had not died accidentally underwater gained momentum.

Dateline: Unforgettable: Why did David Swain murder his wife, Shelley Tyre?

The gist of the Dateline: Unforgettable Episode is the question of motive and method. Shelley Tyre was a well-known school principal who was highly qualified as a diver. She died on March 12, 1999, on a scuba diving trip with her husband, David Swain, at the Twin Tugs site off Tortola.

Initially, the police believed the version of the story David gave when he said Shelley had drowned in a classic accident. Nevertheless, as a result of forensic re-investigations and long-term family advocacy, a years-long investigation was triggered that revealed facts, shedding light on David's intentions and actions.

In Dateline: Unforgettable, we saw how the expert analysis and courtroom testimony raised important details. The dive mask was discovered torn open at the mouth, and one of her fins had been thrust deep in the sand, as though it were forcibly taken off.

Experts testified that the state of the equipment indicated that there was a violent struggle at sea. The civil and criminal proceedings had further shown that the dive shop owned by David Swain was on the verge of serious financial troubles.

As the main breadwinner, Shelley had recently switched jobs to spend more time with David, which reduced the family income and put the business in danger. With a prenuptial agreement in place, David would receive nothing in a divorce; however, in case Shelley died, he would receive everything. This, prosecutors argued, was an obvious financial motive.

Prosecutor Terrance Williams told the jury, as quoted by Oxygen:

“This man here, his wife is killed, and all his dreams came true. All his dreams came true.”

Another aspect of the civil suit filed by Shelley’s parents was that David had been involved with another woman, a chiropractor named Mary Basler. She testified receiving advances from David only a few months before Shelley’s death, and that she had even received emotionally charged letters from him. According to Oxygen, the letter read:

“Life has definitely gotten more complicated… I'm wanting to be with you. I can't change this mess I've got anytime soon.”

Additionally, Christian Thwaites, one of their traveling companions, was present at the unfortunate plunge in Tortola. According to Dateline: Unforgettable, when David Swain returned to the boat without Shelley, Thwaites went into the water himself and saw Shelley’s fin protruding vertically from the ocean floor.

He caught a glimpse of Shelley lying face-up on the ocean bottom, her eyes open. Thwaites rose to the surface, screaming, alerting David. He then rowed over to them and, being a trained EMT, tried to resuscitate Shelley with CPR before finally pronouncing her dead.

However, Thwaites later testified that David gave her an inadequate CPR and even stopped him when he attempted to make more rescue breaths. David reportedly instructed him to cease his attempts, according to Dateline: Unforgettable.

Meanwhile, David Swain’s defense proposed that Shelley might have taken off her fin due to a bruise on her foot and left it standing in the sand to be picked up later. They claimed that once the couple got separated in the water, she could have panicked.

Diving experts explained to Dateline: Unforgettable that panicked divers tend to make irrational decisions, such as removing their equipment, even though they are at a higher risk. The defense also cited prior trip dive logs where Shelley had developed some panic while diving, which they claimed made this explanation plausible.

David was quoted by Oxygen as saying:

“I did not, could not, would not dream of taking the rock of my life out of the world. That’s just … No, I did not.”

At the trials, the Tyre family’s attorneys proved that Swain probably cut off the air supply to Shelley, removed her mask, and submerged her in water until she died. The evidence pattern, the expert underwater reenactments, and the setting of the marriage made both a Rhode Island civil court and, later, a criminal court in the British Virgin Islands believe that the death of Shelley was not accidental.

Swain faced a lawsuit in civil court in 2006 and was convicted in 2009 in a criminal court. He was served a 25-year life sentence for what was described in court as a “near-perfect crime.”

In May 2011, his conviction was overturned after the Eastern Caribbean Supreme Court of Appeals determined that there were flaws in the evidence and trial procedures, namely, improper jury instructions in favor of the prosecution, and that the trial was unfair.

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Dateline: Unforgettable mentioned that the appellate court also claimed that it had taken too long since the death of Shelley Tyre to warrant a new trial, thus releasing David Swain after less than two years in jail.

David Swain moved back to Jamestown, Rhode Island, after his conviction was overturned and spent the next several years living quietly until he died in 2022 at the age of 66.

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