- August 4 – 15-year-old Rebecca L. Reese is raped and murdered in Chantilly by 21-year-old Preston C. Brown.
- August 8 – 19-year-old Gordon Stewart is shanked in the shower at the Lorton Reformatory's Youth Center I by Nathan Price. Stewart is taken to the center's clinic, where he is pronounced dead.
- August 30 – Nine-year-old Veronica R. Covarrubias is fatally injured on the Shirley Highway in Springfield when Mohammed E. Islam falls asleep behind the wheel of his 1973 Pontiac LeMans and crashes into her family's Toyota Corolla at 65 miles per hour just south of the Edsall Road interchange. The five other members of the Covarrubias family are extracted from the Corolla and taken to the Inova Fairfax Hospital, but the car is so thoroughly destroyed that no one notices Veronica still entrapped in the wreckage, which is taken to Franconia Towing and Storage on Vine Street in Alexandria. Veronica's corpse is finally discovered about five hours later, and the lie is told that she died on impact to spare everyone the horror of her lonely death in the crushed car.
- August 31 – While visiting friends, Paul S. Harley is shot to death in a townhouse in the 9600 block of Hagel Circle.
- Bates, Steve. "Death of Va. Girl Called Suspicious." The Washington Post: 0. Aug 06 1990. ProQuest. Web. 6 June 2014.
- Brown, DeNeen L. "Man Convicted of Raping, Murdering Va. Teen." The Washington Post (1974-Current file): 1. Nov 16 1990. ProQuest. Web. 6 June 2014.
- Escobar, Gabriel. "Inmate Stabbed to Death at Lorton Youth Center." The Washington Post (1974-Current file): 1. Aug 09 1990. ProQuest. Web. 2 Feb. 2014.
- Brown, DeNeen L. "Lorton Inmate Convicted in Prison Slaying."The Washington Post (1974-Current file): 1. Nov 14 1990. ProQuest. Web. 2 Feb. 2014.
- Davis, Patricia. "Car Wreckage Hides Body of Va. Girl for 5 Hours." The Washington Post (pre-1997 Fulltext): b01. Sep 01 1990. ProQuest. Web. 4 Feb. 2017.
- "Fairfax Man Slain in Lorton." The Washington Post (1974-Current file): D9. ProQuest Historical Newspapers: The Washington Post (1877-1994). Sep 02 1990. Web. 1 Oct. 2011.
|Fairfax County by Year: 1990|
|July 1990||·||August||·||September 1990|