"Hopeless and incompetent" detective work has thrown a huge question mark over the case against Sarah Payne's alleged killer, a court heard.

Roy Whiting's barrister, Sally O'Neill, made the accusation in the final minutes of her defence closing speech at Lewes Crown Court yesterday.

She urged the jury to "totally disregard" a key piece of evidence which allegedly provides billion-to-one proof it was Whiting, 42, who snatched the schoolgirl from a country lane, killed her and buried her.

The court has been told a single strand of Sarah's hair was found on a sweatshirt recovered from the builder's van when he was arrested at his bedsit in St Augustine Road, Littlehampton, 24 hours after Sarah vanished.

Later in the trial, it emerged the sweatshirt had been among a bundle of 55 exhibits sent up to forensic labs in London in the same van. Among them were two hairbrushes taken from the Payne family home by PC Eric Prior, stray hairs from which were found stuck to the outside of eight other exhibit envelopes.

Miss O'Neill said: "You may find this evidence rather shocking. It's not just that the hopeless and incompetent Mr Prior and the equally incompetent detective sergeant have managed to achieve this degree of contamination of an important exhibit in an important case, it's that nobody seems that bothered about it.

"This is not a fly-by-night bit of defence. This isn't something we have magicked out of nothing to muddy the waters as far as the prosecution's 'compelling' case is concerned.

"It's a serious and very troubling point."

Miss O'Neill said Ray Chapman, who oversaw all of the forensic investigations, had been flippant and dismissive about the finding.

It is the defence case one of these stray hairs somehow managed to find its way from the outside of an envelope on to Whiting's sweatshirt as it was examined in the lab.

Miss O'Neill reminded the jury the hair was not spotted by scenes of crime officer Anna Maxwell when she photographed the garment two days after it was seized. Miss O'Neill concluded: "It's quite possible the hair got on to this sweatshirt as a result of completely shoddy collection of exhibits."

Earlier, the court listened as Miss O'Neill tried to unpick the strands of evidence which the prosecution says can be built up into a picture painting Whiting's guilt in "compelling clarity". She listed the points which, over the past two weeks, have been laid before the jury as pieces of the "jigsaw" gathered by detectives:

Whiting removed the wooden lining from the back of his van to try to remove all traces of Sarah's presence. Miss O'Neill said: "It sounds impressive but it's not actually evidence. Mr Whiting told John Kentish he was going to remove the wood to give himself more seat-room on the Friday before Sarah went missing."

Whiting replaced the rear doors of his van, again to remove traces of Sarah's presence. She said: "There's nothing sinister about changing those doors. The replacement of rusty van doors for new ones comes as no surprise."

Whiting cleaned himself up after abducting Sarah: "This evidence came from Terry Heath who is demonstrably and completely wrong. It demonstrates how much people were prepared to skew their evidence when they realised the nature of the offence of which Roy Whiting was suspected."

Roy Whiting lied to detectives about his movements on the night Sarah disappeared: "It was Roy Whiting who told them about his van. They didn't know anything about it."

A receipt from the Buck Barn Garage, near Sarah's grave site, timed at 9.53pm on July 1: "If Mr Whiting is the right person, it's a pretty bizarre thing to do; to go into a garage and ask for a receipt. It's extraordinary and points to a huge question mark."

Whiting made no comment at interview: "He was advised to make no comment by his solicitor all along."

Three small scratches were found on Whiting's chest and arms when he was examined following his arrest: "This evidence is completely inconclusive."

Whiting was seen rummaging around his van by police who staked out his flat following a visit at 9.30pm on July 2: "That is pure speculation."

Items found in Whiting's van included a spade, rope, masking tape, baby oil, gardening ties and a knife: "Everything can get twisted to suit but there is no evidential basis for it."

Whiting "shook and sweated" when stopped by Detective Sergeant Steven Wagstaff: "His evidence was unreliable. He was gilding the lily."

Miss O'Neill said the only evidence remaining were the 22 links between Whiting and Sarah revealed by fibres found on the girl's shoe and in clumps of hair taken from her graveside.

She turned to the jury and said: "What else in reality do you have? We submit that the complete absence of any scientific evidence, body fluids, fingerprints, anything in the back of the van, is crucial.

"With this sort of extensive fingertip search they would have found something. They kept digging for 18 months and all they came up with at the end of that intensive investigation was fibres."

Miss O'Neill also said her client had done his case more harm than good when he took the witness box.

She said: "Roy Whiting said he was giving evidence because he had nothing to hide. Ironically, it is a curious feature of this case that he would have been in a better position if he hadn't gone into the witness box.

"Do you think it is possible he went into the witness box to do his inadequate best because he has nothing to hide?"

Sarah, eight, vanished from a country lane in Kingston Gorse while out playing with her brothers and sister on July 1 last year. Her body was found 16 days later. Whiting denies kidnap and murder.

The trial continues.

The trial in full: thisisworthing.co.uk