Behind growing criticism of the Italian investigation into the murder of the British student Meredith Kercher lies an energetic campaign by Joe Tacopina, a dapper, top-flight New York lawyer.

Mr Tacopina, who has defended Michael Jackson and Bernard Kerik, the New York City police commissioner, has been retained by the parents of Amanda Knox, one of the three suspects, as a consultant to assist her Italian legal defence.

Six months after Ms Kercher was found dead in Perugia, police have still failed to bring charges against Ms Knox, an American, or the two other suspects, Raffaele Sollecito and Rudy Hermann Guede. All three will appear today before Claudia Matteini, the investigating judge. He was presented this week with a report from three independent forensic scientists.

There is concern that investigators and prosecutors have mishandled crucial evidence. The emerging strategy of lawyers for Ms Knox, from Seattle, and her former boyfriend Mr Sollecito, a wealthy Italian, is to pin the blame exclusively on Mr Guede, an Ivory Coast immigrant, small-time drugs dealer and basketball player who has lived in Perugia since a child.

Mr Tacopina has been at pains in interviews with the American magazine Newsweek and the Italian news magazine Panorama to counter the widespread image in the Italian and British press of Ms Knox as “the angel-faced killer with ice-cold eyes” who indulged in a life of sex and drugs.

He has played down the fact that she has changed her story several times, at one point saying that she was at the flat and heard Ms Kercher’s screams (“a vision” extracted “under duress”), at another claiming that she was at Mr Sollecito’s flat smoking cannabis with him, and at another accusing Diya “Patrick” Lumumba, a Congolese bar owner later released for lack of evidence.

Mr Tacopina questioned the validity of DNA traces found at the flat and on the alleged murder weapon. “I think this girl is innocent. She’s in jail in a foreign country for a crime she claims she didn’t commit,” he said.

“I think the chances of a conviction against Rudy are very high. The evidence puts him at that scene before and after the murder. His bloody hand-print is under the victim’s pillow.”

Lawyers for Mr Guede say that the new forensic science report is consistent with Mr Guede’s assertion that although he had sex with Ms Kercher, it was consensual. Walter Biscotti, one of Mr Guede’s defence team, said that he would sue Mr Tacopina for suggesting in interviews that Mr Guede was the sole killer.

Giuliano Mignini, the chief investigating magistrate, says that the evidence against all three is overwhelming.

The problem for him is that the new 56-page report is at odds with earlier reconstructions of the crime, adding to the impression that initial police declarations of caso chiuso (case closed) were premature.

Despite a steady stream of damning leaks from the investigation to the Italian press, there is confusion rather than clarity over the time of Ms Kercher’s death; whether she was in an alcoholic stupor; how many knives were used to stab her in the throat; who wielded them; and who, if anyone, had sex with her apart from Mr Guede.

Nor has a plausible motive emerged, apart from reports that Ms Kercher and Ms Knox had a history of mutual animosity and had argued over Ms Knox’s alleged theft of cash from Ms Kercher’s bedside drawer to pay for drugs.

When a video of police scientists in white coats examining Ms Kercher’s bloodied corpse was broadcast by a private television network, Ms Kercher’s family were horrified. Again, however, one purpose behind the leaked broadcast was evidently to show that the police had mishandled vital forensic science evidence. But defence lawyers have yet to explain why Ms Knox and Mr Sollecito tried to clean up his flat and the murder scene or why they allegedly simulated a break-in by smashing a window.

Steps in the investigation

August 2007 Meredith Kercher, 21, a University of Leeds student, begins a year-long exchange programme to study Italian in Perugia

November 2 Her half-naked body is found hidden under a duvet in the bedroom of her shared house. Her throat has been cut and the door is locked from the inside

November 6 Arturo De Felice, the investigating police chief, says postmortem results show no evidence of rape, but that sexual assault is suspected. Police announce that they are questioning Amanda Knox, Meredith’s American housemate, as well as Raffaele Sollecito, her boyfriend, and Diya “Patrick” Lumumba, a Congolese barkeeper

November 19 A fourth suspect, dual Ivorian and Italian citizen Rudy Hermann Guede, described as a small-time drug dealer, is named

November 20 Guede is arrested in Germany and is extradited to Italy. Lumumba is freed without charge. The other three deny murder

January 25, 2008 An Albanian witness claims that he saw all three suspects at the house on the night before the murder, and that Ms Knox threatened him with a knife

March 27 Guede, who has already admitted his presence at Meredith’s house on the night of the murder, tells police Knox and Sollecito were also there, Sollecito with a knife

Source: Times archives; agencies

Explore UK News

• Crime News

• Education News

• Health News

• Scotland News

Times Recommends

• Postmen: We bind the nation together
• Tewkesbury: when the memories flood back
• Cast Offs actress: I’m happy that my face fits