IT is probably the single most vital and conclusive piece of evidence in any murder investigation.

The recovery of a victim's body will determine how and when that person was killed and the injuries they have suffered.

But how do detectives prove someone has been murdered and secure a conviction when the body of a missing person has never been found - and is unlikely to ever be recovered?

It was the situation facing officers investigating the "disappearance"

of 32-year-old Southampton mum-of-five Belinda Gibson in February 2002.

Theman leading the inquiry, then Det Insp Jason Hogg, knew in the very early days that she had been murdered at the hands of her husband - but proving it and getting David Gibson and his father Leslie before the courts on a murder charge was to take a further twoand- a-half years.

"It is one of very few cases nationally that has seen a conviction without a body," said Det Chief Insp Hogg, who works in Hampshire's major crime department.

"We had to prove that beyond doubt Belinda Gibson was dead.

That involved building up a picture of her life, looking at who she contacted, the phone calls shemade, the people she regularly spoke to, the shops she visited.

We could see quite clearly that after a certain date - the weekend of February 16-18 - that contact had stopped. She had basically disappeared off the radar."

As part of the massive investigation every single Belinda Gibson listed in the country was contacted.

"We had to make sure she wasn't living somewhere else as herself. We checked all the databases, such as the NHS, DVLA, the AA. There were many places we had to check with and w e h a d to find out how possible it was to change a name and how that process works.

"We had to consider that maybe Belinda Gibson just went away and never wanted to be found - that was David Gibson's line.

"He said that she had told him she wanted to go away - that she needed a break from him and the kids.

"He told us she had come back a week later just to take some things, that she hadwanted to check thingswereOK."

A search of the home they shared together provided no clues and no forensic evidence.

David Gibson had never reported his wife missing but police were alerted after a woman heard third-hand how he had told his neighbour Annamari Weeks that he would kill his wife.

"His daughter r e a l i s e d t h i n g s we r e missi n g i n the house. That was David Gibson moving things around, trying to get rid of the evidence. There was not a trace of her, which backed up the thought she was murdered on that day."

As the murder enquiry progressed andwith still no idea where Belinda's body may be, officers worked against a Presumption of Death chart - a document which lists every enquiry that needs to take place to support the thought that someone is dead.

Det Chief Insp Hogg said: "We would have done anything and listened to any idea that would help us track Belinda down. Every unidentified body in theworldwas checked out by us at the time, just to prove it wasn't Belinda.

"Eventually that proof of death chartwas accepted by the defence at court. It was agreed that Belinda Gibson was dead - it was two-and-a -half years on."

In July 2004 at Winchester crown Court, David Gibson, then 33, of Purvis Gardens, Sholing, and Leslie Gibson, 66, of Mortimer Road, Merry Oak, were jailed for life.

It was put that Gibson senior helped his son suffocate the former hairdresser and then dump Belinda's body in the Solent, off the Needles, weighted down with concrete.

After the conviction David Gibson dramatically admitted to disposing of the body, but denied killing her.

"He thought he had committed the perfectmurder. He had done a lot of research and planned how it was going to work.

"I didn't believe a word David Gibson said from the beginning. He was a liar, someone who told lies to people in his day-to-day life. His motive, I think, was that he didn't want to be with her anymore.

"Infuriatingly I don't think Belinda's family will ever get to know exactly what happened to her or where her body was dumped.

What they do know is who killed her and when.

"This is possibly the best investigation I'veworked on, or everwill. It showed me that there is no such thing as a perfectmurder.

"Nomatter how well someone can plan, how good their witnesses are, how strong their alibi is - every murder can be detected it's just down to getting that little bit of luck."