Contradictions and illogical conclusions in the ruling that freed US student Amanda Knox from jail mean DNA evidence will be re-examined from scratch and witnesses may be re-heard, her lawyer said Tuesday.

"We were very surprised, we took it very badly," Luciano Ghirga said in reference to a damning report released by Italy's highest appeals court explaining why it quashed the acquittal of Knox and her former boyfriend Raffaele Sollecito.

"The new court will re-examine all the evidence from the very start, with fresh expert evaluation and possibly fresh testimony from witnesses," he said.

"We are ready to fight, to answer every challenge point by point," he added.

Knox and Sollecito -- originally sentenced to 26 and 25 years in prison for sexually abusing and killing Knox's British housemate Meredith Kercher -- were acquitted by an appeals court in Perugia in 2011 after four years behind bars.

In March, however, Italy's highest appeals court overturned the acquittal and ordered a retrial in a Florence appeals court, citing "numerous examples of shortcomings, contradictions and incoherencies" in the original appeal ruling.

The 74-page report accused the judges of glazing over clues and insisted the prosecution's claim from the original trial -- that the grizzly murder was the result of "an erotic game that span out of control" -- was a valid hypothesis.

"We had gone beyond that theory, proved there was nothing to it," Ghirga said, while Sollecito's lawyer Giulia Bongiorno added: "If there was an erotic game, most certainly Raffaele Sollecito and Amanda Knox were not part of it."

The report claimed a third trace of blood found on a knife recovered from the house Knox and Kercher lived in should have been examined and was not.

It found fault with the time-scale of the murder the appeals court followed, saying that the "harrowing scream" heard by several witnesses pushed back the time of the crime from between 21:00 and 21:30 local time to two hours later.

It accused the judges of not considering the prosecution's claim that Sollecito's involvement was proved by the fact that only one in three billion people were compatible with the DNA traces found on Kercher's bra strap.

The high court said the confession Knox originally gave police -- of having heard Meredith's screams from another room in the house and covered her ears -- was undervalued. The US student insists the claim was made under duress.

The report also wondered why her initial bid to finger an innocent Congolese barman for the crime held little weight in the appeal verdict.

"Even though she was young, Knox was mature. She was born and raised in a country where one is not allowed wrongly to accuse another person in order to free oneself from a difficult situation," it said.

Kercher, 21, was found half-naked with her throat slashed in a pool of blood in her bedroom in the house that she shared with Knox in November 2007.

A third person, Ivory Coast-born drifter Rudy Guede, who like the other two has always denied the murder, is the only person still in prison for the crime.

The high court faulted the Perugia appeal court for not taking into account the ruling against Guede, which said he could not have acted alone.

Investigators insist that 47 knife wounds on Kercher and the apparent use of two different knives in the attack meant more than one killer was involved.

Both Knox and Sollecito face a retrial in a Florence court, although no date has yet been set and Italy cannot compel the Seattle-born student to return.