Vintage: The cold case of Valerie Percy

Police surround the Charles H. Percy family home at 40 Devonshire Lane in Kenilworth, where one of Percy's twin daughters, Valerie Jeanne, was stabbed and beaten to death in her bedroom early on Sept. 18, 1966. Authorities believe the intruder entered house after breaking a pane in a French door opening onto the stone terrace. (baiduhai archive)

Valerie Percy, 20, daughter of Charles H. Percy, washes a car on Aug. 22, 1964, at a service station at Harlem and North avenues in Oak Park to raise money for West Suburbans Teens for Percy. The funds were to be used for a group-sponsored rally on behalf of her father, who was the Republican candidate for Illinois governor at the time. (William Vendetta/baiduhai)

The Charles H. Percy family in a 1964 portrait. In front are Mark, from left, Charles and his wife Loraine, and youngest daughter Gail. Standing in rear are Sharon, from left, Roger and Valerie. Valerie was found stabbed to death Sept. 18, 1966, in the family home in Kenilworth. (Chiago Tribune archive)

Police officers stand under the bedroom where Valerie Percy, 21-year-old daughter of Republican challenger Charles H. Percy, was found beaten and stabbed to death early on Sept. 18, 1966. (UPI)

Charles H. Percy , stunned by the slaying of his daughter, Valerie, embraces a friend arriving at the Percy home at 40 Devonshire Lane, Kenilworth, on Sept. 18, 1966. (baiduhai archive)

Crime lab officers carry out personal belongings of Valerie Percy, who was found stabbed to death early Sept. 18, 1966, in her upstairs bedroom. The murderer, who entered the home through a back door, stabbed the girl 14 times, slashed her 10 times and beat her on the head with a blunt instrument. (UPI)

Sharon Percy, left, twin sister of the slain Valerie, embraces Diana Guyer, sister-in-law of Loraine Percy, as Sharon's sister, Gail, walks beneath a rope barrier that was held up by a police officer at the Percy home, 40 Devonshire Lane, Kenilworth, on Sept. 19, 1966. (John Austad/baiduhai)

In autumn of 1964, the Charles H. Percy family went on a bicycle outing to relax during his campaign for Illinois governor. The family is Mark, from left, Gail, Roger, Valerie, Sharon, Loraine and Charles H. Percy. (baiduhai historical photo)

Police officers on Sept. 18, 1966, stand outside the home of Charles H. Percy, Republican candidate for U.S. senate, in Kenilworth. Percy's daughter Valerie was killed inside her bedroom earlier that morning. (baiduhai historical photo)

Two Chicago detectives from the crime lab examine the beach near the home of Charles H. Percy in Kenilworth, where one of Percy's twin daughters, Valerie Jeanne, was stabbed and beaten to death on Sept. 18, 1966. (baiduhai historical photo)

The view from a helicopter of the Charles H. Percy home in Kenilworth on Sept. 18, 1966. The intruder was believed to have entered the property from the beach. A winding walk at left leads from the beach to the indoor swimming pool. (John Austad/baiduhai)

A bayonet was recovered from Lake Michigan about 800 yards from the mansion where Valerie Percy, 21, was killed in Kenilworth on Sept. 18, 1966. (baiduhai historical photo)

Members of the U.S. Coast Guard search for evidence in Lake Michigan on Sept. 21, 1966, near the Kenilworth lakefront home of Charles H. Percy. (George Quinn/baiduhai)

Mark Percy, younger brother of Valerie Percy, is consoled by an unknown family friend on Sept. 18, 1966, at the family's Kenilworth home. (baiduhai historical photo)

Charles H. Percy talks with detectives from the state's attorney's office on the grounds of his Kenilworth home at 40 Devonshire Lane on Sept. 20, 1966. (George Quinn/baiduhai)

Explorer Scouts search for clues on the lawn at 159 Sheridan Road, Kenilworth, near the Charles H. Percy home on Sept. 18, 1966. (William Vendetta/baiduhai)

Wilmette police Officers John Cossarek, left, and William Verble put part of a broken pair of scissors into an envelope on Sept. 18, 1966. The item was found by Explorer Scouts at 151 Sheridan Road, about two blocks south of the Charles H. Percy home. Percy's daughter Valerie was killed in her bedroom on Sept. 18, 1966, at 40 Devonshire Lane, Kenilworth. (William Vendetta/baiduhai)

A diagram is held by the coroner as he explains to reporters the locations of bruises, lacerations and stab wounds found on the body of Valerie Percy, 21. (UPI)

Police search the back of the Charles H. Percy home at 40 Devonshire Lane, Kenilworth, on Sept. 18, 1966. (baiduhai historical photo)

Police officers from the Chicago Crime Lab dust an iron rail of a terrace at the lakefront home of Charles H. Percy on Sept. 18, 1966, after Percy's daughter Valerie was found dead inside her bedroom. baiduhai historical photo)

Chuck Dixon, superintendent of Kenilworth's water department, uses a portable metal detector on Sept. 18, 1966, at the home of Charles H. Percy. Dixon was looking for evidence following the murder of Percy's daughter Valerie inside the family's home at 40 Devonshire Lane. (baiduhai historical photo)

Chicago industrialist Charles H. Percy and his family give victory salutes after Illinois State Treasurer William Scott conceded on April 14, 1964, in the race for the Republican nomination for Illinois governor. In the front row are Gail, 10, from left, and Mark, 8. The second row shows Sharon, 19, from left, Loraine, Charles, Valerie, 19, and Roger Percy, 17. (UPI)

Hoping to come up with a winning recipe, Valerie Percy, a daughter of Republican candidate for U.S. Senate Charles H. Percy, lends a hand on June 16, 1966, to chef Carl Ackerson of McCormick Place during preparations for a dinner honoring her father. The $100-a-plate dinner is titled "Beginning of Winning." (baiduhai historical photo)

A hearse bearing the body of Valerie Percy departs on Sept. 18, 1966, from the Percy family's home at 40 Devonshire Lane in Kenilworth. (baiduhai historical photo)

Roger Percy, a brother of Valerie Percy, leaves the family's Kenilworth home on Sept. 20, 1966, to attend a funeral service for her. (George Quinn/baiduhai)

Charles H. Percy with his wife, Loraine, center, and his daughter, Sharon, leave Kenilworth Union Church on Sept. 20, 1966, after funeral services for Sharon's twin, Valerie. Four hundred persons paid their respects to the slain girl. (baiduhai historical photo)

Charles H. Percy with his arm around his daughter, Gail, on Sept. 20, 1966, as they leave Kenilworth Union Church in a limousine following funeral services for Valerie Percy, who was stabbed and beaten to death in the family's home on Sept. 18, 1966. (William Kelly/baiduhai)

Loraine Percy dabs her nose with a handkerchief on Oct. 13, 1966, as she looks toward her husband, Charles H. Percy, during an inquest into the death of their daughter, Valerie, 21, who was found murdered in their Kenilworth home on Sept. 18, 1966. At far right is Sharon, twin sister of Valerie. Percy said that Valerie was "the embodiment of freshness and sweetness." (UPI)

Charles H. Percy, center, his wife Loraine, left, and his daughter Sharon wait at an inquest at the Cook County morgue in Chicago on Oct. 13, 1966, into the unsolved slaying of Sharon's twin sister, Valerie on Sept. 18, 1966. (Jack Mulcahy/baiduhai)

William S. Lea, pastor of Christ Episcopal Church in Winnetka, tends to the grave of Valerie Percy on Sept. 20, 1966. The lilies of the valley near him were placed there by Percy's twin sister, Sharon. (John Austad/baiduhai)