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"Intelligent design" (search) is a religious theory that was inserted in a school district's curriculum with no concern for whether it had scientific underpinnings, a lawyer told a federal judge Monday as a landmark trial got under way.

"They did everything you would do if you wanted to incorporate a religious point of view in science class and cared nothing about its scientific validity," said Eric Rothschild, an attorney representing eight families who are challenging the decision of the Dover Area School District.

But in his opening statement, the school district's attorney defended Dover's policy of requiring ninth-grade students to hear a brief statement about intelligent design before biology classes on evolution.

"This case is about free inquiry in education, not about a religious agenda," argued Patrick Gillen of the Thomas More Law Center in Ann Arbor, Mich. "Dover's modest curriculum change embodies the essence of liberal education." The center, which lobbies for what it sees as the religious freedom of Christians, is defending the school district.

Eighty years after the Scopes Monkey Trial (search), the opening of the trial in federal court marked the latest legal chapter in the debate over the teaching of evolution (search) in public school.

The eight families argue that the district policy violates the constitutional separation of church and state.

About 75 spectators crowded the courtroom of U.S. District Judge John E. Jones III for the start of the non-jury trial. But the scene outside the courthouse was business as usual except for a lone woman reading the Bible.

Arguing that intelligent design is a religious theory, not science, Rothschild said he would show that the language in the school district's own policy made clear its religious intent.

Dover is believed to be the first school system in the nation to require students be exposed to the intelligent design concept, under a policy adopted by a 6-3 vote in October 2004.

It requires teachers to read a statement that says intelligent design differs from Darwin's view and refers students to an intelligent-design textbook, "Of Pandas and People," for more information.

Intelligent design, a concept some scholars have advanced over the past 15 years, holds that Charles Darwin's theory of natural selection cannot fully explain the origin of life or the emergence of highly complex life forms. It implies that life on Earth was the product of an unidentified intelligent force.

Critics say intelligent design is merely creationism — a literal reading of the Bible's story of creation — camouflaged in scientific language, and it does not belong in a science curriculum.

Brown University professor Kenneth Miller, the first witness called by the plaintiffs, said pieces of the theory of evolution are subject to debate, such as where gender comes from, but told the court: "There is no controversy within science over the core proposition of evolutionary theory."

On the other hand, he said, "Intelligent design is not a testable theory in any sense and as such it is not accepted by the scientific community."

Miller also challenged the accuracy of "Of Pandas and People" and said it almost entirely omits any discussion of what causes extinction. If nearly all original species are extinct, he said, the intelligent design creator was not very intelligent.

The history of evolution litigation dates back to the famous 1925 Scopes Monkey Trial, in which Tennessee biology teacher John T. Scopes was fined $100 for violating a state law that forbade teaching evolution. The Tennessee Supreme Court reversed his conviction on the narrow ground that only a jury trial could impose a fine exceeding $50, and the law was repealed in 1967.

In 1968, the U.S. Supreme Court overturned an Arkansas state law banning the teaching of evolution. And in 1987, it ruled that states may not require public schools to balance evolution lessons by teaching creationism.

The clash over intelligent-design is evident far beyond this rural district of about 3,500 students 20 miles south of Harrisburg. President Bush has weighed in, saying schools should present both concepts when teaching about the origins of life.

In August, the Kansas Board of Education gave preliminary approval to science standards that allow intelligent design-style alternatives to be discussed alongside evolution.

Richard Thompson, the Thomas More center's president and chief counsel, said Dover's policy takes a modest approach.

"All the Dover school board did was allow students to get a glimpse of a controversy that is really boiling over in the scientific community," Thompson said.