HARRISBURG -- Michael Behe believes God created the universe but says you need not share his faith to conclude nature is the product of intelligent design.

Dr. Behe, a leading proponent of intelligent design, testified yesterday during a high-profile federal trial that could decide whether public schools can mention the controversial theory as an alternative to the theory of evolution.

A professor of biochemistry at Lehigh University, he was the first witness called to testify for the Dover Area School District, which is being sued by eight families over its policy requiring that a brief statement about intelligent design be read to ninth-graders. The families say the policy supports Biblical creationism and therefore violates the constitutional separation of church and state.

Not so, Dr. Behe testified yesterday. "Creationism is a religious idea; intelligent design is not," he said. "It is a science."

Dr. Behe, whose work includes a 1996 best seller "Darwin's Black Box," is noted for introducing the concept of "irreducible complexity," which says molecular systems are too complex to have evolved, so they must be the product of intelligent design.

"The conclusion that something is designed does not require knowledge of a designer," Dr. Behe said as he began six hours of testimony.

"Intelligent design is a science that proposes some aspects of life are best explained by design," he testified. "It is based on observable, empirical evidence from nature, plus logical inferences."

Dr. Behe finds evidence of design in systems of naturally occurring parts that appear to be arranged for a purpose.

The bacterial flagellum is an example, he said, shining a laser pointer on a diagram in the packed courtroom. The flagellum is a tail-like appendage with parts resembling a turbine, a drive shaft and a propeller, which together operate like a motor, he said.

The theory of evolution doesn't explain the origin of flagella, so they must be the result of design, said Dr. Behe, who is such a controversial figure in the debate over intelligent design that his colleagues at Lehigh posted a disclaimer on the biology department's Web site. "Intelligent design has no basis in science, has not been tested experimentally and should not be regarded as scientific," the statement reads.

Dr. Behe says evolution is testable, but its proponents have not attempted to prove or disprove the theory.

"You can place bacteria lacking a flagellum under some selective pressure and grow then to 10,000 generations," which would take two years, he testified yesterday. "If a flagellum or any equally complex system were produced ... my claims would be neatly disproven."

Dr. Behe was expected to continue testimony today.

The trial began Sept. 26 and is expected to last five weeks.