NEW YORK —An ex-cop accused of running down a family after a day of binge drinking was speeding in his minivan at more than 50 miles per hour, an expert witness in the officer's manslaughter trial testified Friday.

Basing his calculations on the distance the victims were thrown after the collision the night of Aug. 4, 2001, accident reconstruction specialist John Kwasnoski calculated that police officer Joseph Gray, 41, was traveling more than 20 miles per hour above the speed limit before the collision.

Gray, who admits to drinking the day of the accident, slammed into Maria Herrera, 23, her son, Andy, 4, and her sister, Dilcia Pena, 16, underneath an elevated expressway at the intersection of 46th Street and Third Avenue in the Brooklyn neighborhood of Sunset Park.

Victim Maria Herrera's mother, Altagracia Pena Hernandez, in court with other family members

All three died, and a son delivered to Herrera hours after the crash died the next day.

According to prosecutors, a drunk and sleep-deprived Gray ran a red light and hit the family as they stood just 200 feet from their destination, the home of Maria Hernandez, the mother of Herrera and Pena.

Gray, who is facing four charges of manslaughter, could spend up to 15 years in prison if convicted.

A blood-alcohol expert estimated Thursday that Gray could have consumed as many as 18 drinks the day of the crash.

Gray's lawyer, Harold Levy, contends that the collision wasn't Gray's fault, no matter how much he was drinking. Levy has claimed repeatedly that Herrera, who was eight and a half months pregnant when she died, darted out with her family into the path of Gray's 1996 Ford Windstar minivan from between a set of orange construction markers to the left of Gray's vehicle.

Kwasnoski, who has participated in more than 700 accident reconstructions, refuted that theory, however. He testified that the pattern of damage left on Gray's car suggests that the victims were traveling from the other direction — the right, or passenger side — as the prosecution contends.

The expert matched a scrape mark on the bumper that moves upward toward the driver side of the car with a "spider web" impact pattern on the windshield closer to the driver's side of the car.

The collision site

Citing the law of inertia, Kwasnoski recast the dictum, "objects in motion tend to stay in motion," in the context of the accident.

"As the pedestrians were moving and got struck by the vehicle, whichever direction they were moving in they continued to travel in," the expert testified. "There's no physical evidence that indicates any motion toward the passenger side of the car."

Gray's lawyer was hard pressed to refute Kwasnoski's interpretation of the impact pattern on Gray's car, arguing unsuccessfully outside the presence of the jury that the line of testimony unfairly blindsided him.

Prompted by Maureen McCormick, who is assisting Assistant District Attorney Joseph Petrosino, Kwasnoski examined the five shoes found scattered at the scene and selected a pair of black slip-on sandals worn by either Herrera or Pena as those that caused the bumper mark.

Maria Altagracia Pena Hernandez, the mother of both women, wept silently as the expert held her daughter's shoe up for examination.

Levy was, however, able to prompt the expert to admit that "spider web" breakage patterns that occur lower on the windshield, such as the one on Gray's minivan, generally indicate slower impact speeds.

Petrosino will call a medical examiner Monday whose analysis of the injuries to the victims could shed additional light on which way they were heading. Gray is expected to take the stand Tuesday.