HARRISBURG, Pa. -- The second day of a landmark trial over what students should be told about evolution and alternative views of life's origins switched briefly Tuesday into a discussion of faith.

Brown University biologist Kenneth Miller was on the stand Tuesday morning as a witness for eight families suing the Dover Area School District for introducing the concept of "intelligent design."

Miller was asked by a school attorney whether faith and reason are compatible.

"God is the author of nature and evolution is a natural process. The two are compatible," Miller said.

Miller said he believes, "not only that they are compatible, but that they are complimentary."

He had earlier volunteered that he was a practicing Roman Catholic.

Miller co-authored a textbook used by ninth-grade biology students at Dover High School. He opposes the teaching of intelligent design in science classes.

Dover is believed to be the nation's first school system to mandate students be exposed to the intelligent design concept.

The Dover Area School District requires administrators to read a brief statement on intelligent design before classes on evolution.

Eight families have sued, saying the policy in effect promotes the Bible's view of creation.

Tammy Kitzmiller, one of the parents who sued the school district, also took the stand Tuesday and said that the district's intelligent design policy has absolutely harmed her family.

Lawyers for the parents argue that the reading of a four-paragraph intelligent design statement before students hear lessons on evolution amounts to a violation of the constitutional separation of church and state.

The school district says it's not endorsing any religious view and is merely giving students a glimpse of differences in evolutionary theory.

The trial will determine whether a school district should require students to hear about intelligent design.

The non-jury trial is expected to take five weeks.