Homer C. Williams, father of Wayne B. Williams, took the witness stand today in defense of his only child, who is on trial on charges of murdering two young black Atlantans.

The 68-year-old former high school physics teacher said his son, who is 23, has lived in his parents' three-bedroom house all his life, and was never away from them for more than two days until his arrest last June. He said the three members of the family never had much privacy in their modest home.

Homer Williams said he gave his son an electric train set, a bicycle and a combination rifle and shotgun as a boy. He said he took his son hunting and fishing but Wayne "didn't kill very much, so he gave that up."

Williams' parents did not consider him a "failure" when the expenses of running his low-power radio station drove them into bankruptcy in 1976, his father testified.

"I considered that he made progress," the elder Williams said. "A lot of people fail in business. As young as Wayne was, I certainly couldn't consider it a failure."

Williams' trial recessed late today before his father had finished testifying and before cross-examination. Williams' mother and the defendant also are expected to testify before the defense rests its case.

The defense team also made its first direct attack today on the fiber evidence that prosecutors contend links Williams with 12 young black murder victims.

Williams is charged with murdering Jimmy Ray Payne, 21, and Nathaniel Cater, 27, but prosecutors have been allowed to introduce evidence from the cases of 10 other young Atlanta blacks whose deaths were investigated by a special police task force and the FBI.

Randall R. Bresee, a fiber expert from Kansas State University, testified that he performs a battery of eight laboratory tests in addition to basic microscopic examination when he compares fiber samples.

The prosecution's fiber experts testified that microscopic comparisons formed the basis of their conclusions that fibers recovered from the 12 bodies could have come from items in Williams' house or automobiles.

But Bresee admitted under cross-examination that he did not know whether the prosecution experts had performed additional tests. He also admitted that he conducted only one fiber examination in a criminal case and had never testified in court before.

Bresee said he spent less than five hours Wednesday examining fiber evidence in the Williams case at the Georgia State Crime Lab, although he said he usually spends hours, days or weeks examining individual fibers.

A K mart pillowcase that he immersed in the Chattahoochee River for about 30 minutes last Sunday collected "several hundred fibers," Bresee said. Apparently none of the 40 individual fibers he examined matched fibers found on the two victims whose bodies were pulled from the river last spring.

Bresee testified that he found green carpet fibers around the office of defense lawyer Mary Welcome which are "microscopically similar" to fibers found in the green wall-to-wall carpeting in Williams' house. Prosecution expert witnesses have matched fibers found on the bodies of 10 murder victims to the Williams carpet.

Prosecution fiber experts from the FBI's Washington laboratory and the Georgia state crime lab have testified that the fibers in Williams' carpet are unusual and can be distinguished easily by their cross-sectional shape.