Image caption Amanda Knox is serving a 26-year sentence for Meredith Kercher's murder

The DNA evidence which helped convict Amanda Knox of the murder of UK student Meredith Kercher in Italy may have been contaminated, her appeal has heard.

Experts said the collection of DNA evidence fell short of international standards, with police failing to wear the correct protective equipment.

The report was leaked to the media when it was submitted to the court hearing the US student's appeal last month.

Miss Kercher, of Coulsdon, Surrey, was found dead in Perugia in 2007.

A Leeds University student, she was living in Italy as part of a year of study abroad.

Her throat had been cut after what prosecutors claimed was a sex game taken to the extreme.

Knox, 23, and her Italian ex-boyfriend Raffaele Sollecito, 26, are appealing against their convictions.

Knox is serving a 26-year sentence for Miss Kercher's murder while Sollecito was sentenced to 25 years.

Rudy Guede, 21, was also convicted of Miss Kercher's murder in a separate trial and is serving a 16 year term.

Contamination risk

One of the independent experts, who are both from La Sapienza University in Rome, Stefano Conti, said there were several incidents in which forensic police entered the crime scene while not wearing protective masks or hair caps.

He said police often used plastic bags to wrap evidence rather than paper, heightening the risk of contamination.

"There are various circumstances do not adhere to protocols and procedures," he told the court.

The second expert, Carla Vecchiotti, said the genetic profile on the knife's blade that was attributed to Miss Kercher cannot be attributed with certainty.

She said the original testing did not follow recommendations of the international scientific community for dealing with DNA testing.

Ms Vecchiotti said the review concurred with the original tests which found the genetic profile on the knife's black plastic handle could be attributed to Knox.

Both independent experts will be questioned and cross-examined during the next sitting of the court on Saturday.

The hearing will then adjourn until the autumn when a verdict in the appeal is due to be announced.