The Yorkshire Ripper has struck again, killing and mutilating his 12th victim in industrial northern England as he had promised he would in a tape-recorded message to the police there three months ago.

The body of 20-year-old Bradford University student Barbara Jean Leach was found yesterday in the backyard of a rundown rowhouse located near her rooming house, the University and the Manningham red light district of Bradford, a textile mill city in West Yorkshire between Manchester and Leeds.

Police said today the body's mutilation left no doubt that Leach had been murdered by the man who calls himself "Jack the Ripper" in notes to the police and patterns his crimes on the Victorian era's Jack the Ripper, who killed five prostitutes in three months in London's notorious White-chapel District in 1888.

Like Jack the Ripper, who was never arrested and became a figure of legend, the Yorkshire ripper slashes and tears his victims' flesh after beating them to death in a characteristic way the police have not revealed. He has now attacked 16 women in the past four years. Four of them survived despite severe skull fractures.

Nine of the women he killed were prostitutes and all of the bodies have been found in or near neighborhoods frequented by prostitutes in Manchester, Leeds, Bradford and nearby Halifax. Leach, and two of the others he killed, apparently made the mistake of wandering alone too close to red light districts near their homes.

Leach, who was an attractive and popular third-year student in sociology at Bradford University, was on her way home from a pub early Sunday morning when she left some other students to take a walk alone, police said, and never returned to her nearby lodgings.

In a three-minute message on a cassette tape he sent in June to George Oldfield, assistant chief constable of West Yorkshire and leader of a regional task force of 500 police officers hunting the killer, the Yorkshire ripper hinted he would strike again at about this time in Bradford.

"I reckon your boys are letting you down, George. You can't be much good, can you?" He said on the recording, taunting Oldfield for failing to catch him when he committed his last murder in April in Halifax.

"I warned you in March I'd strike again," he told Oldfield. "Sorry it wasn't Bradford. I did promise you that, but I couldn't get there.

"I'm not quite sure when I will strike again, but it definitely will be sometime this year, maybe September or October-- even sooner if I get the time."

The police have determined from expert analyses of his distinctive accent that the killer comes from in or around the towns of Sunderland or Chester-le-Street on the Wear River south of Newscastle in northeastern England, about 100 miles from where his victims have been killed. Police theorize that he may still live in Wearside and do some kind of construction work that occasionally takes him southwest to the area of Manchester, Bradford and Leeds in Lancashire and West Yorkshire.

Police also have from the four survivors a general description of the man -- about 35, tall and rangy, longhaired with a drooping mustache. They have a bootprint from the ground where one of the bodies was found and a saliva sample from the backs of stamps on the letters he sent to them.

The police task force has spent about $6 million and 250,000 man-hours on the hunt, taking statements from 20,000 people. The tape recording sent to Oldfield has been played repeatedly on radio and television and is now being played in police vans touring neighborhoods where it is believed the killer may live or be known.

The killings have revived historical interest in the original Jack the Ripper and prompted one journalist to recall that he may have discovered who he was.

While helping make a television documentary on Jack the Ripper in 1959, Daniel Farson wrote in the Daily Mail, he came across notes on the case made by Sir Melville MacNaghten, then in charge of Scotland Yard.

The notes revealed that Scotland Yard suspected that the Whitechapel murdered was Montague John Druitt, 31-year-old failed barrister and schoolmaster who was alleged, MacNaghten noted at the time to be "sexually insane," MacNaghten ordered the case closed, according to Farson, when Druitt committed suicide after the last and bloddiest of the Jack the Ripper murders.