David Swain, second from right, is escorted to a prison vehicle after being found guilty of murdering his wife in Tortola.

AP / Todd VanSickle

Three years ago after a civil jury in Providence had found him responsible for his wife’s death, David Swain, a onetime Jamestown councilman and dive-shop operator, stood in the emptying courtroom and told reporters he “would welcome a criminal trial” someday to clear his name. At least then, he said, “all evidence gets evaluated.”

Warwick lawyer J. Renn Olenn, who had pursued the wrongful-death case against Swain for four years by then, stood nearby listening as Swain spoke. Olenn was there again Tuesday, in a criminal courtroom in Tortola, when another jury — this one with Swain’s life in its hands — found him guilty of murdering Shelley Tyre 10 years ago while on a scuba-diving vacation.

Yesterday, in sight of the green Caribbean waters where Tyre drowned, and a few miles from the hilltop prison where Swain returned after Tuesday’s verdict, Olenn recalled that moment in Providence on a February day in 2006.

“He told the newspapers that once he got his chance to tell his story, and that when all the facts came out, it would be clear he couldn’t have committed this crime,” Olenn said in a telephone interview. “Well, he got a chance to say everything he wanted to say, and explain every question that ever existed. From what I could see, it was completely rejected by the jury.”

It was only by chance that Olenn, who drew the blueprint that Tortola prosecutors followed over the last three weeks to convict Swain, ever entered the case.

His wife, Mary, and Tyre’s father, Richard, were acquaintances who shared an appreciation of art history. One day in 1999 — four months after Shelley’s drowning — the Olenns visited the Tyres in Jamestown to drop off a museum booklet. The Tyres related the inexplicable loss of their daughter, an expert scuba diver, whose marriage to Swain, her friends knew, was in trouble. Olenn outlined his expertise in investigating aquatic deaths. He offered to take a look at Shelley’s death, which Tortola officials had then ruled an accident.

“It was then just two parents helping each other,” he said. “That went on for a little more than a year until I was able to assemble the evidence that this was very likely murder. I didn’t start out looking for that, but when I discovered it was murder, it became a lawsuit.”

That lawsuit, which ended in a jury awarding Tyre’s parents almost $4 million in damages, forced Tortola officials to reopen the case.

Late Tuesday afternoon, in the cool confines of the narrow courtroom in Tortola, the Tyres and the Olenns held hands as they strained to hear a soft-spoken jury foreman say the word: guilty.

The nine-member jury unanimously found Swain had murdered his wife of almost six years, accepting the prosecution’s — and Olenn’s — theory that he had done so to collect hundreds of thousands of dollars in insurance and other assets while pursuing another woman, and while knowing that a nuptial agreement prevented him from profiting if they divorced.

“I had, at that point, no feeling at all,” Olenn said. “When the verdict was read, [the Tyres] finally had what they needed, and I must say I was thinking about them.”

Olenn said he believed it was the prosecution’s expert witnesses — the same witnesses he had used in his successful civil case — which persuaded the jury in the circumstantial case that Tyre, 46, had no pre-existing conditions that might have caused her to panic, as the defense tried to suggest, and that her death could be nothing else but murder.

Those witnesses included a designer of diving equipment, a pathologist who dove the site where Tyre died, and a premier researcher in the United States — with over 60 years experience in diving medicine — who calculated how much air from her tank Tyre had used prior to her death.

Together those experts “represented over 200 years of diving investigation, science and medicine,” said Olenn. “Every one of those people was convinced it could only be murder, it could not be an accident. Even the defendant’s witnesses conceded they could not rule out murder.”

Swain, now 53, and Tyre had traveled to Tortola with another couple and their young son for a week of scuba diving. Olenn and Tortola prosecutors theorized that Tyre died about eight minutes after she entered the water with Swain on the last full day of diving.

They suggested Swain climbed onto Tyre’s back when they had reached the wrecks of two tugs in about 80 feet of water, and turned off her air until she had drowned. In the struggle, Tyre’s dive mask strap was broken, the mouthpiece of her snorkel fell off and Tyre had jammed one of her swim fins into the sand toe-first. A dive-shop owner who had rented equipment to the vacationers found Tyre’s broken equipment the next day at the site.

The dive’s time sequence was a critically important point, Olenn said, and Swain’s own testimony may have worked against him.

“His testimony was it took them a minute or two to get down the mooring line, took them about four or five minutes to swim to the wrecks, and then it took five to ten minutes to visit the wrecks,” before the two divers separated, as Swain said they often did. Using that time sequence, said Olenn, “when she took her last breath, he was with her.”

Swain, who has always maintained his innocence, said he never knew what happened to his wife after they separated. Her body was discovered and brought to the surface by Christian Thwaites, Swain’s vacationing friend, who entered the water after Swain surfaced alone.

Olenn said Swain’s defense team presented their own expert witness who arrived at a different air-use calculation which supported Swain’s claim that Tyre was alive when they separated under water. But that witness, said Olenn “changed his calculations over the weekend, and when he came back on Monday, they were really absurd … The jury didn’t buy it.”

Swain’s witness, Glen Egstrom, a retired kinesiology professor from the University of California, Los Angeles, also reportedly acknowledged under cross-examination that Swain’s reports to authorities after the dive were inconsistent at times.

Swain is expected to be sentenced Nov. 4. He faces life in prison in Tortola. He is reportedly considering appealing the verdict to the Eastern Caribbean Supreme Court. His two Boston lawyers, Jeffrey Denner and Timothy J. Bradl, did not return telephone calls Wednesday.

Olenn says he’s exhausted from what became a promise to see justice done. “The verdict to me was something I always believed in.”

He says he will be available if Tortola officials need his help again if there is an appeal. “But I don’t think they will.”

tmooney@projo.com