Detectives identified a man they say raped two women, and killed one of them in the late 1980s and early 1990s.
Montgomery County Police said Kenneth Earl Day - who died at the age of 52 in March 2017 in Upshur County, West Virginia - was responsible for both attacks.
Police said Day first attacked a 52-year-old woman as she walked on Lewis Avenue in Rockville on June 25, 2989. He approached her from behind, assaulted her and raped her, officials said.
The second attack happened on Oct. 3, 1994. Police said they believe Day assaulted and killed 42-year-old Dr. Le Bich-Thuy. She was found to the side of her home in the 1600 block of Martha Terrace in Rockville. Police said she had been assaulted, raped, and then strangled.
At the time, investigators told WUSA9 they believed Thuy was followed to her home from the Twinbrook Metro station, then struggled with her killer at her front door before being dragged to the side of her home.
The DNA samples collected from both scenes did not match anyone in the national DNA database known as CODIS.
To solve the crime, police partnered with Parabon NanoLabs, a DNA company in Virginia that specializes in DNA phenotyping, or the process of predicting physical appearance and ancestry from unidentified DNA evidence.
They made a composite photo of what the suspect would have looked like based on the DNA evidence left at the scene. They also submitted a genetic data profile to the publicly available database, GEDmatch.
Cold case investigators said they did additional investigation – including genealogy research – to identify Day as the suspect of the rapes and murder.
Detectives got a sample of Day’s DNA from his autopsy and matched it to the suspect’s DNA profile taken as evidence from both crime scenes.
Police are still investigating Day and believe he may have been involved in other unsolved crimes. They released photos of him, as well has his previous addresses, in hopes they will get tips from the public.
The murder victim, Thuy, worked in immunology research at the Children's Hospital in Washington D.C.
"She really did have one of the best scientific brains that I've encountered," a coworker told WUSA9 in 1994.
And in the end, science was the key to helping solve who killed her.
Anyone with information about Kenneth Earl Day is asked to call the Montgomery County Department of Police – Major Crimes Division, Cold Case Section at 240-773-5070. Callers may remain anonymous.
Prior known addresses for Kenneth Earl Day with approximate dates:
- 1989: 500 block of Beall Avenue, Rockville, MD 20850
- 1988: 100 block of Willowdale Drive, Frederick, MD 21702
- 1990-1991: 20000 block of Frederick Road, Germantown, MD 20876
- 1990: Unit block of Whetstone Drive, Gaithersburg, MD 20877
- 1992: 11700 block of Zebrawood Court, Germantown MD 20876
- 1993-1994: 12300 block of Selfridge Road, Silver Spring MD 20906
- 1994-2000 block of Baltimore Road, Rockville, MD 20851
- 1997-1999: 14400 block of Belvedere Drive, Woodbridge VA 22193
- 2002-2004: 11800 block of Renner Road, Keymar, MD 21757
- Late 2000’s: 10300 block of Mumma Ford Road, Rocky Ridge, MD 21778
- Late 2000’s: Unit block of Heavner Grove Road, Buchannon, WV 26201
