A medical forensic expert for U.S. State Department Special Agent Christopher Deedy will not be able to tell a state jury that he believes shooting victim Kollin Elderts had cocaine in his system and was high when he died, a judge ruled Monday.

Deedy, 30, will be standing trial for murder a second time because his first trial last year ended with the jurors deadlocked. He testified that he fatally shot the 23-year-old Elderts in a Wai­kiki McDonald’s restaurant on Nov. 5, 2011, in self-defense.

Elderts’ autopsy did not reveal the presence of cocaine in his blood. It did, however, reveal the presence of alcohol and benzoylecgonine, a substance the body produces when it processes cocaine. The concentration of alcohol was 0.12, 1.5 times the legal threshold for drunken driving.

A test of fluid in Elderts’ eyeballs revealed the presence of cocaethylene, a substance the body produces when it processes cocaine and alcohol at the same time.

Deedy wanted forensic pathologist Jona­than Arden to testify in trial that the presence of benzoylecgonine and cocaethylene in Elderts’ system indicates Elderts was high on cocaine at the time of the shooting but that the cocaine cleared from Elderts’ system after he died.

Circuit Judge Karen Ahn ruled Monday that Arden can testify only that cocaethylene gets into a person’s eyeballs through the bloodstream and that cocaethylene can have the same, but less potent, effect on a person as cocaine.

Arden and a state expert testified in a pretrial hearing Wednesday that benzoylecgonine does not affect the human body in the same way as cocaine.

Testimony that Elderts was high on cocaine at the time of the shooting could have helped Deedy’s lawyers portray Elderts as the first aggressor and bolster Deedy’s claim of self-defense.

The retrial could start as early as Thursday.