A British backpacker jailed for rape has had his conviction quashed after new DNA evidence suggested he may not be guilty.

Scott Harry Richardson, 26, was found guilty of sexually assaulting a 23-year-old American woman at a house party in Redfern, Sydney, in December 2015.

The 'Y-filler Plus' test, which was not available at the time of the trial, is a very effective way of analysing complicated evidence and sexual assault samples that contain small amounts of male DNA in large quantities of female DNA.

Scott Harry Richardson (pictured) was found guilty of sexually assaulting a 23-year-old American woman at a house party in Redfern in 2015

During the original two-week trial, the court heard the alleged attack occurred while the woman was sleeping under a blanket on a couch in the early hours of the morning, following an 'impromptu' party at Mr Richardson's apartment.

The woman claimed she woke up to find her assailant on top of her, and when she told him to stop, she said he replied with 'This is what you want, isn't it? This is what you want?'.

At the time, Mr Richardson told the court he did not rape the woman, but rather it was a case of mistaken identity.

He claimed he jumped onto her thinking she was his friend. But after realising his mistake, he got off and said 'sorry' before leaving the room.

A crucial piece of evidence relied upon by the prosecution was a sample collected from the woman's vagina, which was found to include Mr Richardson's DNA as a result of 'Y-filler' testing.

Mr Richardson's lawyers argued the DNA was due to 'secondary transfer', which suggests DNA can be transferred as a result of simple skin to skin contact, such as a handshake. But the New South Wales district court rejected this claim.

Mr Richardson met the 23-year-old woman at a house party in Redfern in December 2015

The 'Y-filler Plus' test, which was carried out by Forensic Science SA, maps 27 markers on the Y chromosomes unlike the 'Y-filler' test used by Forensic Analytical Science Services (NSW), which only maps 17 markers

As a result of the findings, Mr Richardson was found guilty of two counts of sexual intercourse without consent and is currently serving a minimum two year and three month jail sentence.

Now, the Court of Criminal Appeal has quashed his conviction after hearing that the DNA sample has undergone more rigorous 'Y-filler Plus' testing, which revealed there were two male DNA profiles compared to the original test that showed one.

Unlike the 'Y-filler' test used by Forensic Analytical Science Services in NSW, which only maps 17 markers, the superior 'Y-filler Plus' test, which was carried out by Forensic Science SA, maps 27 markers on the Y chromosomes.

The court found the test provided additional 'credible', 'plausible' and 'compelling' information, which could have allowed Mr Richardson to mount a different defence, The Daily Telegraph reports.

Lawyer Nick Hanna said the results of the 'Y-filler Plus' test in this case may encourage NSW laboratories to adopt the testing process currently available to them.

'This appeal represents a watershed moment for criminal investigation in NSW and, more generally, Australia,' Mr Hanna told The Daily Telegraph.

'I expect that many people who have been convicted of crimes in cases where the police relied on DNA evidence may now seek to use this superior testing method to launch appeals similar to … Mr Richardson.'