Police found blood on a handrail at the home of four Idaho student murder victims and more on a glove outside. 

The samples came from two unidentified but different men. Prosecutors say those samples shouldn’t come into play at trial if the defense intends to argue that they suggest a mystery man stabbed the undergrads to death and not the defendant.

Idaho prosecutors are asking a Boise judge to block Bryan Kohberger’s defense from arguing an “alternative perpetrator” theory unless he can first prove it’s relevant to the case under the state’s rules of evidence.

Defense attorney Anne Taylor visits the King Road crime scene on January 3, 2023. The house was the scene of a quadruple homicide in November 2022, with the victims all being students at the University of Idaho.  (Derek Shook for Fox News Digital)

Edwina Elcox, a Boise-based defense attorney who is following the case, predicted the defense would use that evidence to “muddy the waters” and try and show reasonable doubt at trial.

Kohberger’s highly anticipated trial is scheduled to begin on Aug. 11.

He could face the death penalty if convicted.

Before he was granted a change of venue, Latah County Judge John Judge entered not guilty pleas on Kohberger’s behalf at his arraignment in May 2023.