Washington's defense asked Judge Michael Aloi to dismiss the indictment for prejudice caused by "unnecessary prosecutorial delay".
The defense argued that many of the witnesses who were interviewed 40 years ago are now deceased, others can't be located, and evidence has been lost or destroyed.
The court went into an executive session to discuss the matter. Washington will appear in court again at 9 a.m. on Tuesday.
Criminal complaints said Washington and another man, Phillip Reese Bush, shot and killed Guy Phillips, Wanda Phillips, and William Cobb nearly 40 years ago. The bodies of the three victims were discovered at Windmill Park in the Jackson Addition area of Fairmont. Lawn keepers found the bodies in an open field inside the city park in the morning hours of August 2, 1974.