John Jackson and his wife, Rebecca, operate the Turin Shroud Center of Colorado in Colorado Springs, giving frequent seminars on the shroud and continuing research into it.

Rebecca Jackson said she and her husband "happen to believe that the shroud is for real. But we're open to the fact that possibly it's not."

John Jackson was among the group of the 1978 Shroud of Turin Research Project scientists who spent more than 100,000 man hours and more than $5 million examining the cloth with everything from X-rays and microscopes to ultraviolet and infrared light. He also worked with scientists at NASA's Jet Propulsion Laboratory to examine the shroud with a device that detects light signals and is normally reserved for examining pictures taken by space probes. The result was a 3-D image, rather than a photographic-like negative.

Rebecca Jackson said since she got involved in her husband's work back in 1990, she's seen a growing interest in the shroud.

"It used to be that 99 percent of people looking at it were Catholic. Now it's about 60 percent Catholic and 40 percent others. There's greater overall Christian interest versus seeing it as a Catholic relic."

At least one academic has been openly skeptical of it in recent months.

Nathan Wilson, a literature fellow at New St. Andrews College in Moscow, Idaho, created a news media stir earlier this year when he said he had been able to recreate an image on linen similar to the shroud by painting an image on a plate of glass, covering a length of linen with the glass and exposing it to the sun for an extended time.

He maintained at the time that his experiment, which he emphasizes on his Web site was "crude," showed the shroud was likely a forgery. He said last week his views remain "very much the same, but I'm a lot more cynical about the integrity of the whole discussion. I've seen enough now to know that both sides are very much slanting their positions and their data.

"I think the discussion is fundamentally faith-driven. It's difficult for people (to step back) when they are pretending it's a logic-based discussion rather than faith-based discussion," he said. Yet he concedes that as a scholar of literature, there are scientific principles he isn't an expert on.

Eventually he would like to do a follow-up experiment, "for my own sake, just with some older handwoven linen because it's very difficult to come by. But something that more accurately reflects the age and is as finely woven as the shroud." He'd like to repeat the experiment under hand-blown glass as well, noting a medieval forger using his method would have had access to that type of glass.