The defense has rested in the trial of a crime-scene investigator accused of tampering with evidence in a double-murder case.

Douglas County CSI chief David Kofoed opted not to take the stand Friday as the trial wound down. He offered no explanation for his decision.

Closing arguments are still expected before the case is handed over to the judge for a verdict. Kofoed opted not to have a jury trial.

Prosecutors say Kofoed planted a speck of a victim's blood in a car to bolster a case against two suspects. Those two men were charged, spent months in jail and were later cleared in the killings of a Murdock couple in 2006.

Kofoed's attorney argues accidental cross-contamination explains how blood got in the car.