The blue Chrysler minivan came barreling down Lenox Avenue, leaving the police in its wake on Tuesday morning.

A gunpoint robbery had happened just minutes before, leading the police to stop the minivan and take the driver into custody. But then another suspect in the minivan grabbed the wheel and took off, going at least twice the speed limit for 20 blocks. The getaway lasted barely a minute.

The Chrysler minivan plowed into a Honda with a mother and son inside, then spun around and hit three pedestrians, including Sister Mary Celine Graham, 83, a nun who died of her injuries.

The frantic episode — which resulted on Wednesday in a murder charge against the man police say drove the minivan — prompted some onlookers to question police tactics regarding vehicle pursuits. Witnesses said they saw an unmarked police car about a block behind, its lights flashing and its siren blaring.

But the police account, pieced together from radio transmissions and reports, makes clear that responding officers did not have time to give chase, and that the unmarked police car began its pursuit only two blocks before the Chrysler crashed.

“Police cars did go south behind the car, but they were at least a block away,” Police Commissioner Raymond W. Kelly said. “I wouldn’t consider that a close pursuit. I would consider it appropriate police tactics. It was an unfortunate series of events that caused a nun to lose her life.”

Despite the perception that the police eagerly engage in such pursuits, there are patrol guidelines governing chases.

The New York Police Department’s guidelines lay out a number of factors, like the nature of the offense, that officers and their superiors must consider when deciding whether to pursue vehicles. The time of day, population density and weather also come into play.

The policy requires breaking off pursuits “whenever the risks to uniformed members of the service and the public outweigh the danger to the community if the suspect is not immediately apprehended.”

A patrol supervisor and a commander must direct the pursuit and stop it if conditions warrant. Certain tactics are prohibited, including ramming, placing a police vehicle in a position to be hit, driving alongside the pursued vehicle and setting up roadblocks. (The last comes with the caveat that a supervisor may direct otherwise.)

The episode Tuesday unfolded in nine minutes, the police said. Two robbers stole a BlackBerry and $23 from an 18-year-old, who called the police and described the men and the blue minivan.

Minutes later, the police stopped a minivan 20 blocks north, on West 142nd Street. They had pulled the driver out and begun to handcuff him when a second man in the vehicle took the wheel and sped off.

Sixty seconds later, the Chrysler crashed into the other minivan at West 122nd Street. A handgun was found in the Chrysler.

William Robbins, 18, who was arrested before the crash, was charged with robbery. The driver in the crash, identified by the police as Dyson Williams, 20, was arrested Wednesday and charged with murder and robbery.

(Source: NY Times)