Former Yankee, Jim Leyritz, is currently on trial in Florida for DUI manslaughter. On Wednesday the prosecution called as an expert witness a law enforcement official (Officer Buttery) who tested Leyritz’s sobriety the night of the incident.

But defense attorney David Bogenschutz submitted several decisions to the judge, which indicated other courts have also refused to admit HGN evidence, because it is as not established science.

In other words, HGN is a clue cops use to identify suspects. It isn’t evidence. It’s just a clue, a hint.

The prosecution had hoped to ask Officer Buttery about the results of a test called the Horizontal Gaze Nystagmus test (HGN test), which he conducted on Leyritz. The test looks for eyeball quivering, which often indicates intoxication (both drugs and alcohol).

Apparently, however, the HGN test is usually employed only to establish probable cause in advance of demanding that a suspect take a blood-alcohol test. It isn’t used as evidence of intoxication.

Outside of the jury’s hearing, Officer Buttery was asked how often he has been qualified as an expert in a circuit court. He said he never had been. He was then asked how many times judges had rejected him. The answer was hundreds of times.

Sidebar: The prosecutor in this case continues to shoot herself in the foot. First, she questioned one of her own witnesses about the victim’s sobriety, after the judge had ruled that the defense could not do so. Then, she asked the medical examiner about the blood test he conducted that showed the victim’s blood-alcohol level was 0.18, higher than Leyritz’. After that she asked the ME questions that probably hinted to the jury that the victim was thrown from the car and killed only because she was not wearing a seatbelt—another fact the judge ruled inadmissible.

Why Is HGN Junk Science?

The HGN test results are nonspecific. The HGN test is proof neither of drug use nor alcohol use. It can hint to some sort of brain problem, including a concussion (which I’d guess is frequent in car wrecks). It’s not proof of any specific level of intoxication, such as the the blood-alcohol level of the test subject.

An individual cop’s perceptions are the only “record” of the HGN test results. In other words, a cop swears that he or she saw an eyeball wiggle but has no proof that the eyeball really did wiggle. Squad car videos aren’t close ups; they can’t show the wiggle.

An HGN test doesn’t prove the subject was legally drunk.

An HGN test isn’t science; it ought to be legally junk.

Judge Gold Knows Statistics

Judge Marc Gold conducted voir dire on Buttery outside the jury’s hearing. The defense attorney tried to show that Buttery wasn’t a scientist and therefore not an expert. The prosecutor tried to show that Buttery had expertise in the HGN test, simply because he had been trained by scientists. And then she asked him whether he was an expert.

He said, “No. I’m not an expert.”

At that point, the judge pointed out to the prosecutor that the witness had said he wasn’t an expert, but he had some questions for him nonetheless. He asked the witness what the margin of error of the test was. Buttery said in his experience he had concluded some test subjects had a blood-alcohol level of 0.06 and the level had turned out to be as high as 0.08 and as low as 0.04.

Judge Gold promptly disallowed Buttery to testify as an expert. He said, “0.02 is a 25% margin of error. That’s unacceptable.” Apparently the judge has taught statistics.