Skeptics also point out that experiments have shown that it's easy enough to self-inflict with razors or even chemicals that leave a wound-like marking on the skin or produce a blood-like liquid.
One of the most controversial Christian artifacts, the so-called Shroud of Turin, is believed by many to have wrapped the body of Jesus Christ after his crucifixion.
The 14-foot-long, 3.5-foot wide cloth is marred with burn and water marks, holes, patches and, some say, blood stains. But the shroud also displays the shadowy image of a man, which some say is clearer in a photonegative than in person.
While some believe the cloth is the burial cloth of Jesus, others argue that it is a forgery.
"Every responsible and legitimate scientist who knows anything about the shroud accepts it as an artistic representation made during the 14th century," says Steven Schafersman, administrator of the Skeptical Shroud of Turin Web site.
But other experts say if it's art, it isn't consistent with other art created at that time.
"It is just out of character with any art that one finds from the Middle Ages, Renaissance," says Ian Wilson, author of "The Blood and the Shroud."
The first reports of the shroud date back to the 14th century, when a French crusader who had just visited the Holy Land brought it home, according to National Geographic. The crusader gave it to a church in Lirey, France and Christians from all over the area came to gaze at the artifact.
Later, the shroud moved to Turin, Italy, where it still protected in the Cathedral of St. John.
While the Church guards it as an important Christian artifact, scientists still debate its authenticity.
Tests completed in 1988 determined that the cloth dates back to the 13 or 14 century, far too late to actually be the burial cloth of Jesus.
But in 2004, Raymond Rogers, a scientist with the Los Alamos National Laboratory said the threads that were actually tested came from patches used later to repair the shroud after a fire. He said the shroud could indeed date from Jesus' era but he died soon after publishing his findings.
It's the underlying premise of one of the most popular religious thrillers of all time.
In Dan Brown's best-seller, "The DaVinci Code," the protagonist uncovers a secret society called the Priory of Sion, created to protect Christianity's deepest secret: Jesus married Mary Magdalene and fathered a child.
"Jesus and Mary Magdalene were not only an item, but also she was actually his successor," said Lynn Picknettt, co-author of "The Templar Revolution."
Though the four gospels of the New Testament describe Jesus as unmarried, Picknett and others say competing gospels discovered in Egypt in 1945 tell a different story.
Those "Gnostic gospels," they say, contain evidence that Jesus and Mary Magdalene might have been married – possibly, with children.
"The DaVinci Code" also cited another source: Documents discovered in a French library in 1975 detailing members of the Priory of Sion and its purpose.
Later, however, these documents were exposed as fake, when it was learned that the man who "discovered" them created them and planted them in the library.
"There is absolutely no proof that there was any Priory of Sion or any secret society that was founded to protect a secret about the bloodline of Jesus Christ," said Sharan Newman, author of "The Real History Behind the DaVinci Code."
National Geographic Channel's "Touched by Jesus?" premieres Monday, March 29, 2010 at 8 p.m. ET/PT. For more information, click here.