A federal appeals court, criticizing errors by a controversial Alexandria judge, has ordered a new trial for a Woodbridge carpenter who contended he was injured when a nail-driving device misfired.

The 4th Circuit Court of Appeals decision, made public yesterday, said District Judge Oren R. Lewis "abused his discretion" when he "severely restricted" testimony by an expert appearing on behalf of carpenter Chris Garrett during the two-day trial in June.

The appellate court said Lewis, an 80-year-old, semiretired jurist, also erred in his instructions to the jury on whether Garrett's failure to wear protective safety goggles contributed to the mishap. Garrett said he was injured in one eye when the device, similar to a handgun, misfired. A six-member jury rejected Garrett's claims and ruled in favor of the firm that made the device.

The appeals court decision, written by Judge Sam Ervin III, turned aside a complaint by Garrett about Lewis' "persistent questioning of and comments to the witnesses," a frequent criticism by lawyers who appear before Lewis.

"While Judge Lewis certainly did participate to an uncommon degree in the questioning of witnesses," Ervin said, his behavior in the Garrett trial did not match earlier instances in which the higher court ordered new trials because of Lewis' constant interrogation of witnesses.

The same appeals court recently ordered a new trial in a medical malpractice case heard by Lewis for what it called the judge's "glaringly" improper courtroom decisions, "disparaging" and "improper" comments and progovernment bias.

In the Garrett case, the court said, Lewis "severely restricted" testimony by an expert, Navy Cmdr. Alfred I. Cipriani, preventing Cipriani "from giving his opinion on the ultimate issue in the case, i.e., whether the stud driver was negligently manufactured" by Desa Industries Inc.

The appeals court said Cipriani, who holds a graduate degree in mechanical engineering and is a registered engineer, was qualified to give such an opinion, contrary to Lewis' ruling.

The court said Lewis also improperly blocked Cipriani from referring to photographic blow-ups of diagrams of the device, despite a pretrial ruling by another district judge approving the photos.

Lewis also refused to give jury instructions requested by Garrett on the question of safety goggles.

"Since Desa did not demonstrate that Garrett's eye injury could have been avoided or would have been less severe had he been wearing the goggles, the requested jury instructions should have been granted," the court said.