It started as a routine stop: Some jerk had his feet up on a subway seat and two cops gave him a ticket.
But this was no ordinary seat hog.
When the transit officers ran his name through a database, a more serious offense came up — he was sought for questioning in a murder.
Gregory White, 43, of East New York, Brooklyn, was suspected in the January slashing death of his girlfriend, Coney Island grandmother Victoria Hammond, 58.
Pulled by sheer luck from an A train at Columbus Circle on Wednesday, White allegedly confessed at Coney Island’s 60th Precinct station house and was charged with second-degree murder on Thursday.
“Wow. On the A train. Wow,” the victim’s son, Dartaguan, 38, of Waterbury, Conn., said when told how cops found the suspect.
“They followed through and did not give up,” the son added. “They did a great job.”
Other family members were shocked to hear that White’s bad subway etiquette led to his arrest.
“We had hope that somebody was going to pay for this,” said the victim’s former husband, Eric Hammond, 66, of Brooklyn.
Victoria Hammond had been stabbed two dozen times, law-enforcement sources told The Post.
Police are giving little credence to White’s alleged claim that she had lunged at him — while naked — with a knife, which he says he pulled from her grip and stabbed her with in self-defense.
White was arraigned Thursday night on charges of murder and criminal possession of a weapon.
Taking up more than one seat isn’t even a crime — it’s a disorderly-conduct offense under Section 1050.7, Subsection (j) of the Public Authorities law.
But police argue that “broken windows” policing is effective in dissuading larger crimes and catching bigger fish.
“Addressing quality-of-life stuff led to the arrest of this murderer,” one law-enforcement source said.
“You never know who you’re going to encounter when you’re enforcing these relatively minor offenses,” said another law-enforcement source.
“You can’t take anything for granted,” the source said, noting that at least eight times in the past year, turnstile jumpers have been stopped and found to possess guns.
Meanwhile, on Thursday transit cops confronted a homeless panhandler and later learned that he was wanted for two crimes, including one in which he allegedly stole $25 from a young woman at an ATM and then threatened to sexually assault her.