60 years later, the murder of Valerie Percy in Kenilworth, Illinois remains unsolved

A murder in Chicago's most affluent suburb happened 60 years ago, long before anyone had ever heard the phrase "cold case." Today, it's one of the coldest cases in the Chicago area.

Valerie Percy, the daughter of longtime U.S. Sen. Chuck Percy, was brutally killed in the family's home in north suburban Kenilworth just weeks before her father was first elected to office.

In the home stretch of her father's campaign, someone broke into the family home and stabbed and beat Valerie to death. To this day, the 21-year-old Cornell graduate's murder remains unsolved.

"Nobody seems to have a final answer as to what happened to this young lady," CBS News Chicago legal analyst Irv Miller said.

The first murder in Kenilworth history happened at 5 a.m. on Sept. 18, 1966, on the second floor of the Percy mansion along Lake Michigan.

"Valerie was an unlikely victim who was murdered in an unlikely place at an unlikely time on an unlikely day with an unlikely weapon," said Glen Wall, author of "Sympathy Vote: The Reinvestigation Of The Valerie Percy Murder."

The sound of broken glass sent Valerie's stepmother to her room.

"She was stabbed to death and beaten in her bedroom. Percy's wife, who was Valerie's stepmother, woke up and confronted the killer in the house before he ran out," Wall said.

In the days that followed, it became a national story as investigators began questioning dozens of Valerie's acquaintances.

Her father paused, then re-started his campaign for Senate; winning, some say, in part because of the murder.

"The notoriety of the Percy family and the fact that it was the only murder in 75 years [in Kenilworth] drew a lot of attention," Wall said. "People thought there was a sympathy vote. … It, of course, referred to Chuck Percy getting votes out of sympathy for the murder of his daughter."

Chuck Percy would serve three terms in the U.S. Senate representing Illinois, leaving in office in 1985. He passed away in 2011, never knowing who killed his daughter.

All the while, Kenilworth police have kept details and case files largely out of the public eye, declining most Freedom of Information Act requests on the case, claiming it remains an active investigation, leading some to allege a coverup.

"It doesn't hold weight, because the law requires that an active investigation be protected from being disclosed to not only the general public, but potentially the person that did it," Miller said. "They want to solve it, they want a suspect, they want to clear the case, and they want somebody to go to court, and if they are telling the world what evidence they have, that hinders the investigation."

Sixty years later, the killer could still be alive, but the Kenilworth police case very much is, as is the decades-old intrigue over who killed Valerie.

"Forevermore. There's no statute of limitations on a murder in Illinois," Miller said.

There have been lots of allegations over the years about who was behind this murder, from the mob to serial killers, but no allegations have ever been proven.

In a statement, Kenilworth Police Cmdr. Ryan Glew said the department said it is "currently investigating open and active leads into the 1966 homicide of Valerie Percy."

"Bringing closure to the Percy family and the community remains a priority for the Kenilworth Police Department. Due to the ongoing investigation, the department cannot comment further," Glew added.