A remarkable pro bono offer to solve 18 DNA samples which could explain what happened to Madeleine McCann – first made in the nine.com.au podcast Maddie – has so far been met with deafening silence from UK police in charge of the years-long, $20m hunt for the missing girl.

The London detective who heads up Operation Grange - DCI Nicola Wall – has not yet acknowledged correspondence from one of the world's top DNA scientists, weeks after she was informed how ground-breaking testing methods in the US could breathe new life into the cold case.

Nine.com.au has provided a series of forensic reports from the UK lab that tested the McCann samples in 2007, the Forensic Science Service (FSS), to top American scientist Dr Perlin for review.

Asked what he had seen in that FSS documentation, Dr Perlin said: "What this report says is there is a possibility that Madeleine McCann's DNA is present in this mixture."

Following an investigation by nine.com.au , Dr Perlin on April 5 sent a formal request to London Metropolitan Police’s DCI Wall to assist Operation Grange, the investigation she has led since 2014. DCI Wall, an experienced homicide investigator, has so far not responded to Dr Perlin.

Despite several approaches from nine.com.au , DCI Wall has declined to explain why Dr Perlin appears to have been stonewalled by Scotland Yard.

Over the weekend, following revelations first aired in nine.com.au's podcast investigation into Madeleine's disappearance, an army of UK tabloids lined up to report on Dr Perlin's offer.

Detective Chief Inspectors Nicola Wall and Andy Redwood arrive at Faro's Police Station during an investigation on Madeleine McCann case on December 11, 2014 in Faro, Portugal. (Getty)

In recent episodes of Maddie , multiple requests to Scotland Yard, the UK Home Office and the office of Prime Minister Theresa May to comment on Dr Perlin and the impact his work could have on the Madeleine mystery have all been refused.

Dr Perlin's Pittsburgh laboratory Cybergenetics has a proven history of helping police forces in Great Britain, with his team and technology contracted to assist UK law enforcement on various cases over the past 20 years.

Dr Perlin has informed DCI Wall he will analyse the 18 McCann samples of interest for free, and that he could deliver the results back to Operation Grange in just one week.

The computational testing methods pioneered by Dr Perlin, known as TrueAllele, is far superior to the methods used in 2007 to analyse evidence from the McCann holiday apartment and a rental car.

Cybergenetics chief scientist Dr Mark Perlin has pioneered tremendously powerful software to solve extremely complex DNA evidence. (Supplied / Credit: Andrew Rush)

Dr Perlin told the podcast the 2007 testing methods at the FSS had "failed" in the McCann case, effectively closing off potentially important lines of inquiry.

"Computers have no dog in the fight," Dr Perlin said, explaining how TrueAllele works. Cybergenetics only requires the archived DNA data from UK police, not the actual DNA samples.

"If your goal is truth, and your goal is the best science, then there is really no excuse for not opening up the data for better analysis by better methods.

"True Allele has been used successfully in England and Australia and Northern Ireland in cases like [the Madeleine McCann mystery] where there are complex mixtures and a small amount of DNA."

Police photographs of McCann rental car where forensic and DNA samples were taken from. (Supplied)

Dr Perlin said he would find it strange to not deploy hugely improved DNA technology to work on cold cases where there were "inconclusive" DNA samples waiting to be solved.

"It would be as if you found some old tissue from a person's body from one hundred years ago and now we have better microscopes so we can analyse it with. And some governmental agency says, 'No, let's only use the methods from 100 years ago that we know don't work. They failed then, they can fail now. And better methods with stronger microscopes or electron microscopes that could answer the question that we have, let's not use them’."

Ten months after DCI Wall took over Operation Grange, the police investigation was drastically scaled back, with the number of officers on the team cut from 29 to four.

The Home Office is currently considering a request from Operation Grange for further funding, believed to be £300,000, through to March 2020.

Portuguese police had focused on the McCann hire car and certain areas inside the family's Algarve holiday apartment after intensive search work by two specialist British cadaver dogs, three months after Madeleine went missing.

The two dogs had alerted inside the apartment, car and on several personal family possessions. Any alerts by cadaver dogs need to be corroborated by additional evidence, such as DNA.

Diagram showing where cadaver and blood dog alerted inside apartment 5A, where Madeleine McCann's family stayed. (Nine)

One month after the dogs had searched those areas, Madeleine's parents were declared arguidos, formal suspects.

Mr and Mrs McCann, both doctors from Rothley, Leicestershire, have strenuously denied they were involved in the disappearance of their daughter, and nine.com.au does not suggest any involvement on their part.

Arguidos status was lifted from Mr and Mrs McCann when the Portuguese police investigation was shelved in August 2008.

Aged three when she vanished in May 2007, Madeleine would turn 16 in 2019.

Maddie podcast investigation of Madeleine McCann disappearance. (Nine)