Giving gruesome details in a chilling, detached manner, Dennis Rader, 60, explained to a Kansas court how he would "troll" for his "projects" during his time off as a dog-catcher. Dressed in "hit clothes", he carried a "hit kit" which included ropes and other items. "I had project numbers," he said. "If one didn't work, I'd move on to another."

Describing his first killings, in 1974, of a couple and their two children, Rader said: "I had never strangled anyone before, so I really didn't know how much pressure you had to put on a person or how long it would take."

Over the next three decades Rader played cat and mouse with the media and authorities, leaving cryptic messages and anointing himself with the initials BTK - "Bind, Torture, Kill".

In one note to local news outlets, Rader asked: "How many do I have to kill before I get my name in the paper or some national attention?"

The former president of a Lutheran church council and a boy scout leader yesterday revealed at length the conditions under which he murdered his first family, Joseph and Julie Otero, aged 38 and 34, and their children, Josephine, 11 and Joseph, 9. He came through the back door and cut the phone lines, then told them he was hungry and wanted a car.

"The whole family just panicked on me," he said. "I worked pretty quick. I strangled Mrs Otero. She passed out. I thought she was dead. I strangled Josephine. She passed out. I thought she was dead. Then I went over and put a bag on Junior's head."

Unsure whether Mrs Otero was dead, "I went back and strangled her again". He took Josephine to the basement where he hanged her and then masturbated by her body.

Rader went on to terrorise the Wichita area throughout the 1970s. While his victims appeared to be chosen at random, his method of murder was consistent. He said "sexual fantasies" were his driving force.

He would cut telephone lines, break into homes, tie up his victims and force them to suffer a slow death.

In 1980 it seemed the BTK killer had disappeared, raising speculation that he had died or moved on. He reappeared a few years later only to disappear again in 1991.

He re-emerged last March, sending a letter to the local newspaper with pictures of a victim he strangled in 1986, Vicky Wagerle, along with a photocopy of her driving licence, and claimed responsibility for the murder. Until then her death had not been linked to BTK.

Rader was arrested after his daughter, Kerri, 26, reported that her father might be the killer.

Police asked her for a voluntary blood sample. They found it was a 90% match with BTK. They placed Rader under surveillance. When they arrested him on February 25 he came "without fuss" after they pulled him over in his car.

His confession, on what would have been the opening day of the trial, came as a shock to prosecutors.

He told the judge that he understood the charges against him and had waived his right to a jury trial. "The defence worked with me real well. We went over it. I feel like I'm pretty happy with them."

Rader will not face the death penalty because the crimes were committed before Kansas adopted a new law on capital punishment.

When sentencing takes place on August 17 he is expected to be imprisoned for the rest of his life.