Experiments by a forensics expert suggest that a knife found near Robert Wone’s dead body had been planted there, but a judge must decide whether to consider the tests in determining the fate of the men accused of covering up the slaying.

The knife is a key part of prosecutors’ case that Joseph Price, 39, Dylan Ward, 39, and Victor Zaborsky, 44, covered up Wone’s stabbing death in their Dupont Circle town house on Aug. 2, 2006, when Wone was spending the night. Prosecutors say the three — charged with obstruction of justice, tampering with evidence and conspiracy — used a towel to spread Wone’s blood on the knife as part of a cover-up.