Opening statements began Tuesday in the trial of an alleged drunken driver accused in the death of a Nassau police officer.

James Ryan, of Oakdale, is accused of causing a chain-reaction crash that led to the death of Officer Joseph Olivieri, who was killed on the Long Island Expressway in October 2012.

Prosecutors say Ryan, 28, was driving drunk and caused two accidents to which Officer Olivieri responded. Soon after, the driver of a Cadillac Escalade, who was driving through the crash scene, fatally struck Olivieri.

Ryan's defense attorney Marc Gann says the only person to blame is the driver of the Escalade. Prosecutors acknowledged that the driver was going through the crash site at 40 mph when he had to swerve to avoid Ryan's disabled car and struck Olivieri.

Prosecutors decided the Escalade driver's actions were not criminal, and he received immunity when he testified before the grand jury that indicted Ryan.

The prosecution is expected to call the driver of the Escalade to testify Wednesday.

Ryan was charged aggravated vehicular homicide and vehicular manslaughter. He faces up to 25 years in prison if convicted.