CHICAGO – Authorities said yesterday they are investigating whether the shooting deaths of a federal judge’s husband and her frail, 89-year-old mother were the work of white supremacists out for revenge.

The killings came a month before white supremacist Matthew Hale was scheduled to be sentenced for trying to have the judge, Joan Humphrey Lefkow, killed over her handling of a trademark dispute involving his hate group.

Police said they were looking at the possibility the crime was committed by hate groups but cautioned that it was “but one facet of our investigation.” Still, from the federal courthouse to the family’s neighborhood, the talk was about Ms. Lefkow’s involvement in the white supremacist case.

“There is much speculation about possible links between this crime and the possible involvement of hate groups. We are looking in many, many directions, but it would be far too early to draw any definitive links,” said James Molloy, Chicago’s chief of detectives.

The judge and other members of her family were placed under federal protection after the killings.

On Monday, the judge came home to discover the bodies of her husband, Michael Lefkow, 64, a lawyer, and her mother, Donna Humphrey, in the basement of the Lefkows’ North Side house.

A federal source who spoke on condition of anonymity said the victims had been shot in the head. Another source said that police found two .22-caliber casings and that a window at the house had been broken.

The two victims would have been easy to overpower. Lefkow family friend Thomas Robb described them as “very vulnerable people,” explaining that Joan Humphrey, who was visiting from Denver, needed two canes to walk. Michael Lefkow had undergone surgery last week to repair a ruptured Achilles tendon and was on crutches, he said.

“All of us are horrified by the murder of Judge Lefkow’s husband and mother. Nothing can prepare us for such a stunning, tragic event,” said Charles Kocoras, chief federal judge for the Northern District of Illinois.

Hale’s father, retired East Peoria policeman Russell Hale, dismissed the notion that his son may have been involved in the slayings, saying he is under constant surveillance by authorities.

“There would be no way he could order anything,” Mr. Hale said. “It’s ridiculous.”

By yesterday morning, news articles of the killings had been posted on white supremacist Web sites, along with “RAHOWA!,” meaning “racial holy war.”

In a discussion on a white nationalist Web site in 2003, members had posted the Lefkows’ home address. Anti-Defamation League official Mark Pitcavage said another white supremacist’s short-wave radio show last April had discussed killing the judge.

Investigators looking for a motive for the slayings searched for clues from the judge’s professional life, including her role presiding over cases involving Hale and others.

During Hale’s murder-plot trial, prosecutors contended that he was furious when Ms. Lefkow ordered him to stop using the name World Church of the Creator because it had been trademarked by an Oregon religious group that has no ties to Hale.

Hale, 33, is awaiting sentencing April 6 for the murder plot. Police would not say whether they have attempted to talk with him.

As recently as last year, federal authorities took the murder plot seriously enough that they provided Ms. Lefkow with protection for at least a few weeks, and Chicago police stepped up patrols of her neighborhood. The Lefkows took their own security measures, installing cameras on their front porch, said Michael Miner, a longtime friend of Michael Lefkow.

Michael Lefkow was active along with his wife in the Episcopal Church, and they had four daughters plus a fifth from his previous marriage.