Scientists took one step closer to declaring the Shroud of Turin an authentic human burial sheet, though not necessarily that of Jesus Christ or anyone living in his time. Scientists studying the religious relic, which believers say is the burial wrap of Christ, have reached a working hypothesis about how the image of the human face on the cloth might have been formed.

The official report of the Shroud of Turin Research Project has now been released, and concludes after scores of chemical and photographic tests that the cloth image is not a forgery. "We can conclude for now that the shroud image is a real human form. It is not the product of an artist," the report said.

While the cloth can never be proved to be shroud of Jesus, scientists have been working for a decade to test whether anything about the cloth is authentic. Beginning in 1978, some 30 scientists formed the ad hoc research group to travel to Turin to examine the famous shroud. The cloth itself is a 14-by-4 foot sheet that bears a very faint, straw-colored image of the front and back of a bearded man.

The image is so faint, however, that it appeared little more than vague stains until high contrast photographs revealed sharp detail in the image.

Though the most important test of all is yet to come, the dating of the shroud by the classical carbon tests of archeology, the scientists so far believe that they have now ruled out a number of previous theories.

Scientists now believe that the archbishop of Turin will allow carbon dating as soon as techniques which can use only minute samples of the cloth can be perfected. Until recently, carbon dating would have required destruction of a large piece of the shroud.

"We have pretty well ruled out several popular theories," said Barrie Schwortz, a photographer who was on the scientific team that traveled to Turin. "The hand-painted theory has been pretty much dispelled," he said, as well as the possibility that the image could have been the scorch marks of a metal statue exposed to a fire while wrapped in the cloth. He said the image was also inconsistent with the hypothesis offered by some believers that a burst of radiation from the body might have marked the cloth.

"The most popular theory with the group, and the working hypothesis now is that the image was formed when the oils from the skin touched the surface of the cloth and adhered to it. The oils would, over time, discolor the cellulose in the cloth," Schwortz said.

"It would be like taking a white handkerchief and rubbing it on your face, then putting it away in a drawer for a few hundred years. It would come out discolored, and most discolored in the area where your skin oils touched it," he said.

To duplicate such a process, scientists held cloth to parts of their bodies and then subjected the material to artificial aging, primarily by heating it. The tests did produce images, and those of the fingers looked much like the finger images on the shroud.

But the process failed to reproduce the fine detail in the face on the shroud. Wrinkles and even hairs of the beard are visible in the shroud image.

The chief reasons why such an image could not have been painted, according to the scientists are: The image adheres only to the very top of the cloth fibers and is so thin that it would be extremely difficult to duplicate with any material that might be painted on. No chemicals characteristic of paint have been found in close analysis. And the image, when run through a computer analysis, is found to be a perfect match for an image that would be made by laying a cloth over a body, with the cloth touching in the right places and receding in the right places.

The research group's report was released for the opening of an exhibit at the Brooks Institute of photography in Santa Barbara, Calif.

The shroud has been an object of veneration among Christians for most of the six centuries that it has been known to exist. It first surfaced in France in about 1350, the property of a knight who may have obtained it as loot from the crusades to Palestine. Its authenticity has been questioned ever since.