Updated

A New York man is about to go on trial in vehicular homicide case that tests the limits of criminal consequences. He wasn't behind the wheel when a police officer was struck and killed -- he was leaning against the guardrail.

Prosecutors say James Ryan was charged because his drunken driving on the Long Island Expressway set in motion a series of events that ended in the officer's death. Nassau County Police Officer Joseph Olivieri was struck and killed after arriving to investigate a pair of accidents Ryan allegedly caused in October 2012.

The crashes have already been the subject of vigorous court battles, including an appeals court decision supporting the 16-count indictment. But Ryan's attorney believes prosecutors have overreached.

"I think the district attorney's office has been blinded by the allegations of alcohol use," said defense attorney Marc Gann. "There's nobody else to criminally blame so they blame Ryan. ... It's extremely unusual for a person not driving to be charged with a vehicular death."

Ryan, a 28-year-old part-time student, could face up to 25 years in prison if convicted of aggravated vehicular homicide, manslaughter, driving while intoxicated and other charges. A spokesman for county prosecutors declined comment, citing the upcoming trial.

"This factual situation is certainly rare and relatively unique," said Joseph McCormack, an adjunct law professor at St. John's University who serves as the New York state traffic safety resource prosecutor.

McCormack said prosecutors are employing the legal principle of "causation/foreseeability," in which suspects are charged in events that are foreseeable results of their actions. In one such case from 1994, a New York City man was convicted of murder in the death of an officer who was had been chasing after him in a robbery investigation and fatally fell through a skylight.

More recently, in 2013, Nassau prosecutors convicted a man of vehicular manslaughter for the death of a motorcyclist who crashed into his wrecked car after he crashed while driving intoxicated.

According to prosecutors, Ryan's Toyota first clipped a BMW on the expressway, stopped farther down the road in the high-occupancy lane and then was hit by another car. A few minutes later, an SUV driver apparently did not see Ryan's vehicle, which had been turned sideways from the earlier crashes, and smashed into Ryan's car before hitting Olivieri.

Prosecutors say Ryan had been drinking in a Manhattan bar and at the time of the accidents had a blood-alcohol level of 0.13, above the state's 0.08 threshold of drunkenness.

A state judge initially dismissed the charges, finding Olivieri's death was "solely attributable" to the SUV driver, who was never charged.

A state appeals court later reinstated the charges, saying it was "reasonably foreseeable that the defendant's conduct would cause collisions and that the police would respond and be required to be in the roadway, where they would be exposed to the potentially lethal danger presented by fast-moving traffic."

It also noted Ryan's actions "need not be the sole cause of death and, indeed, the defendant need not have committed the fatal act to be liable."

Leonard R. Stamm, a Maryland attorney and dean of the National College for DUI Defense, did not agree with that ruling.

"It appears that the appellate court took a much broader view," Stamm said in an email. "It is not reasonably foreseeable that driving drunk would cause that kind of fatal accident."