The cold-blooded killer of PC Ian Broadhurst had been on the run from police in the US for nearly a decade when he shot dead the Bradford traffic policeman.

Bieber was wanted for allegedly setting up the contract killing of Markus Mueller, 29, in February 1995 and the attempted murder of his estranged girlfriend Michelle Stanforth in August of that year.

Police interrogated him after the death of Mueller, who had been convicted of importing steroids, but did not charge him. Investigators said Bieber and Mueller were competitors in selling illegal steroids and both were in love with Stanforth.

The authorities in the US investigating Bieber said today they may well consider extraditing him to face charges for his alleged crime.

Cherie Avery, spokesman for the Lee County attorney's office in Florida, said: "We are looking at it and we are waiting to for all the legal documentation from England. Once we get it we will make a decision."

If US authorities want to prosecute Bieber there could be a complication because the UK will not allow prisoners to be extradited to places where the death penalty could be used.

Bieber began using steroids in the early 1990s and made a quick impact at bodybuilding shows. In 1992 he won the Southeast NPC Southeastern USA men's light heavyweight championship.

He was also successful in other sports, setting a state record for swimming the 100 metres backstroke when he was 13 and playing American football for the Green Wave varsity for two years.

The son of a head teacher, Bieber, 38, grew up on a palm-lined street in Florida. He spent his summers in the swimming pool and the winters playing American football.

But the happy-go-lucky teenager's life changed for the worse when he developed a keen interest in bodybuilding after leaving school. He began using steroids and then started to sell them and as he slipped into a life of crime he became more violent.

After leaving Fort Myers High School he spent a year in the Marines before being discharged after taking unauthorised absence. He learned how to use handguns and was trained to use an M-16 rifle, being described as an "average" marksman.

Days after his first marriage - to the former girlfriend of Markus Mueller - a hitman shot Mueller dead and targeted Ms Stanforth, but missed.

Police arrested the killer, who was jailed, but they suspected Bieber had ordered the 1,000 dollar shootings and issued a warrant for his arrest.

The marriage broke down and in early 1996 Bieber travelled from his home town Fort Myers to Georgia where he obtained Nathan Wayne Coleman's birth certificate which he used to get a false identity card and passport.

In September that year he slipped into England through the port of Ramsgate and began living in Selby. In March 1997 he married again after meeting Denise Horsley in a nightclub but the marriage lasted only 12 months. He then moved to Leeds, moving into the Springwood Road flat in November 1999.

Bieber became a registered doorman, working at pubs and clubs in Leeds, York, Wakefield and Batley and was also employed by security companies. He was known to be a regular gambler at casinos and betting shops, went to the gym daily and won karate trophies.

But a neighbour in Leeds described him as "sullen and rude."

Ronald Moss, 82, alerted police that an American man was living alone just round the corner from where the getaway car had been abandoned.

Mr Moss said his neighbour was always well-dressed in a jacket or suit. But he said: "He lacked manners. I did him a favour and he hardly said thank you. He was sullen and spoke very little."

Bieber's father, retired school principal Frank Bieber, a Korean War veteran, who last saw his son in September 1995, said: "David was a natural athlete. He was a nice, quiet young man. Who thought it would turn out like this?"

He said becoming hooked on steroids was the beginning of the end for his son.

Neighbour Ronald Moss, a retired jeweller, who had lived ten yards from Bieber in Springwood Road, Leeds, for four years said he first noticed Bieber because he parked on the pavement.

He said: "Bieber was always working on the car - a real old banger - and was always dumping rubbish out the windows. I told him I was the unofficial environment officer for the area and asked him to keep things tidy. I thought he was going to get violent and he just turned away. I ended up picking up the litter. But he was never in any way aggressive."

Bieber's second wife, Denise Horsley, told police he was a gambler and keep-fit fanatic with an interest in martial arts and survival techniques.

She said he behaved as though he was always on the run, dyeing his hair different colours and living out of a suitcase. She became suspicious of him and even searched the internet to see if he was wanted but found nothing.

Former schoolfriend Sean Kirkpatrick said: "He was very athletic. He was friendly, not a person who had any hostilities at all. He set incredible records in the physical tests for athletics.

"He was naturally gifted. Something changed along the way. It's sad the way he turned out, it ultimately broke up his mother and father's relationship."