A Port Jefferson Station man pleaded not guilty on Monday to a slew of charges that include murder and driving drunk, three months after a wrong-way crash that killed another driver.

Authorities allege 54-year-old defendant Christopher O’Brien was impaired and driving an Audi A4 east in the westbound lanes of Sunrise Highway two days before Christmas when he hit a Toyota Corolla head-on in the left lane shortly after 5:30 a.m., killing driver Thomas D’Eletto, 57, of Aquebogue.

“At the scene, police observed that O’Brien was unsteady on his feet, had bloodshot, glassy eyes and was slurring his words, and he gave oral admissions to the police about drinking and driving,” Suffolk County District Attorney Tom Spota said in a statement.

Police at the crash scene, just east of Horseblock Road, charged the suspect with driving while intoxicated, the DA’s office said, and a blood test two hours after the crash showed a blood-alcohol content of 0.17 as well as cocaine.

While D’Eletto was pronounced dead at the scene, O’Brien was treated for non-life-threatening injuries at Brookhaven Memorial Hospital Center in East Patchogue.

According to Spota, another driver allegedly saw the defendant drive into oncoming traffic three times about 20 minutes before the fatal crash, at a location north of the Long Island Expressway.

“Then on Sunrise Highway, several drivers reported to police they had to go onto the median or the shoulder of the road to avoid a collision with O’Brien,” Spota said.

The DA’s Office said O’Brien has been remanded to jail for the now numerous charges, from an indictment unsealed Monday, which include second-degree murder by depraved indifference; aggravated vehicular homicide; second-degree manslaughter; second-degree vehicular manslaughter; first-degree reckless endangerment; aggravated driving while intoxicated; driving while intoxicated; driving while impaired by a drug; driving while impaired by the combined influence of alcohol and a drug; and reckless driving.

O’Brien’s attorney, Hauppauge-based Scott Gross, called the crash a “significant tragedy” but maintained his client’s innocence.

“We’re going to evaluate the evidence,” he said in a phone interview Tuesday, “take a look at what the prosecution provides and then make our determination as to how to proceed from there.”

Gross added that the DA’s office had until recently pursued the case as a misdemeanor and said that would not have been true if it had a strong case.

“Their delay is indicative of provability issues,” the attorney said.

O’Brien is due back in court before State Supreme Court Justice Fernando Camacho on April 4.