It certainly is Chicago's most enduring crime question. The victim Valerie Percy would have turned 70 years old this year. She was killed at age 21, as she slept in her family's Kenilworth home during the 1966 U.S. Senate campaign.
The police case is still open, but FBI records obtained by the I-Team and a new investigative book point to a prime suspect.
There had never been a murder in Chicagoland's richest suburb. That changed, literally, overnight at 5 a.m. on September 18, 1966.
Millionaire businessman and soon-to-be U.S. Senator Charles Percy and his family are awakened by shattering glass, then muffled groaning. Percy's daughter and campaign manager Valerie had just been struck and stabbed; her killer quickly running off toward the lakeshore. No one has ever been charged.
But tonight, hundreds of pages of publicly unseen FBI records obtained by the I-Team reveal a prime suspect. This man: William Thoresen III, son of a Kenilworth industrial tycoon; described in one FBI report as "violent," a "mental case...armed and dangerous."
In the posh north suburb of Kenilworth, Percy's home was just a block and a half away from the house where Thoresen grew up and frequently returned for family visits in the mid-60s.
"If you can think of a person who is just mad at everyone and mad at the world and lashing out constantly he was perfect for that. Um so ya know a lot of instances going back to his teen years was just crazy," said Glenn Wall, Percy murder researcher.
After his own investigation, Chicago native Glenn Wall reports in this new book numerous uncanny connections between Thoresen and the Percy case. Most significantly, authorities believe the murder weapon was a serrated bayonet. Thoresen had been arrested in Chicago and Los Angeles for aggravated assault and possessing illegal weaponry.
"He had 70 tons of weapons including everything up to Howitzers, a laundry list of weapons that he had and bayonets are in there," said Wall.
In Lake Michigan three days after the murder, authorities found this bayonet, seen here in an evidence photo obtained by the I-Team. Even though there were footprints from the Percy home to the beach, in 1966 authorities never scientifically connected the prints nor the bayonet to the killing. Nor were they able to trace this single glove found near the scene, being shown here tonight for the first time. After the murder, FBI records reveal it was Thoresen's Los Angeles probation officer who brought him to the attention of Chicago police.
ABC7's Chuck Goudie asks: "And he called the FBI in LA and said?"
"And he said that I believe this person should be considered a suspect in the murder," said Wall.
Records show when authorities finally found Thoresen in New York, he said "he could be of no help in the Valerie Percy case and refused to be interviewed or answer any questions about the Percy case or any other matters."
Four years later, Thoresen was shot and killed by his wife, who beat the murder charge by telling jurors her husband had admitted killing several people.
"You have a highly violent person confessing to murders he was never convicted for any of those crimes but all those people disappeared," said Wall.
Goudie asks: "So as you sit here today are you convinced that he did it?"
"I think of the line from All the President's Men. One of the sources in that story said 'I can't positively prove that this person did it, but I can come pretty close,'" said Wall.
Kenilworth police tonight say Thoresen "was never cleared from involvement in the Percy case" and that his possible involvement is now considered "undetermined."
They ask anyone with information to call the Kenilworth Police Department at 847-251-2141.