The police investigation into the murder of Meredith Kercher is focusing on the three arrested suspects' movements at the time of her death.

Italian police are scouring CCTV footage taken near the cottage where the student's bloodstained body was found. Detectives are also trying to pinpoint where mobile phones belonging to Raffaele Sollecito, Amanda Knox and Patrick Diya Lumumba were used.

Questions surrounding their whereabouts hinge on how their stories relate to each other and images of people leaving and entering the house where the 21-year-old woman was killed.

Police are trying to establish whether Patrick Lumumba was at the till of his bar, Le Chic, in Via Alessi in Perugia, on the evening of the murder, as he claims.

New witness 'saw Meredith suspects together'

Amanda Knox, Raffaele Sollecito and Rudy Guede were see at the house in Perugia where the American student died

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• Murder in Perugia

Background

• Meredith Kercher: Q&A

• New DNA not from Meredith suspects

• Timings crucial to Kercher murder investigation

Related Links

• Meredith 'grabbed murderer's hair'

If he was, could he have left to reach the cottage on Viale Sant' Antonio that Ms Knox and Ms Kercher shared, about ten minutes walk away, and returned?

According to Italian media reports, Romano Mero, a Swiss professor visiting Perugia at the time, has told police that he left his hotel to eat a pizza at 8.30 on the evening of November 1. By 9pm he was at Le Chic, and he says that Patrick was behind the bar. Professor Mero, however, had reportedly earlier told police by phone that he was at the pub for two hours, from 8pm to 10pm.

The change in his testimony is crucial, since police say a signal trace on a mobile phone owned by Mr Lumumba was recorded in the area of the cottage at 8.38pm.

Mr Lumumba told police that he had opened the bar "about 5.30 or 6pm", but witnesses have said it was closed when they passed it at 7pm.

Mr Lumumba said his Senegalese friend, Usi, arrived at the bar at 8pm, but Professor Mero says he remembers Usi arriving about 10pm. Usi himself has said that he arrived later, at about 10.40pm.

The first till receipt was issued at 10.29pm (in Italian bars payment is usually made before consumption of food or drink, but in pubs or bars where the customer is known to the owner the bill is sometimes presented only when the customer leaves).

Records show Mr Lumumba sent a text message to Amanda at 8.18pm - which he allegedly later deleted - and she replied "See you later" by text at 8.35pm.

He claims that his message simply told her that there were not many customers at the bar and she was not to bother to come in to help, as she usually did on Tuesdays and Thursdays, and that her "see you later" was a general reply on the lines of "see you around", not an assignation.

Police believe they met shortly afterwards at a basketball court between the University for Foreigners, where both Ms Knox and Ms Kercher were studying, and the cottage.

However, lawyers for Mr Lumumba say he could not have left the bar, taken part in an attack on Meredith and returned within the time frame.

Detectives are also trying to establish the exact time of death of Ms Kercher and how it relates to the stories of their suspects.

Sophie Purton and Robyn Butterworth, two friends of Ms Kercher, have told police that all three had had an early supper of pizza, ice cream and coffee at Robyn's flat "at about 6pm", drinking only water and no alcohol (forensic tests on Merediths body have confirmed this).

They then watched a film on DVD, "The Notebook", until "about 9pm". Ms Purton has testified that she then walked home with Ms Kercher, but their ways parted and she went to her own home, leaving Ms Kercher to walk the 500 yards to the cottage in Viale Sant' Antonio. This would put Ms Kercher's return to the cottage at about 9.15pm.

Pathologists at first put the time of her death at between midnight and 2am. They later revised this because of analysis of the food in her stomach, which was only partly digested, suggesting that she was killed sooner after eating her meal.

Investigators are reportedly to re-question Ms Purton and Ms Butterworth to double check the time they had supper. The provisional time of death, meanwhile, is between 9pm and 11pm, although the fatal blow could have been struck earlier since Ms Kercher bled to death slowly.

Ms Knox's account of her movements are also being studied very closely. She has changed her story several times, first saying that she spent the evening and night with her boyfriend Raffaele Sollecito, then admitting she was at the cottage but only heard Ms Kercher's screaming from her bedroom while Mr Lumumba was in it, then reverting to her original account and claiming that she was not at the cottage at all until the next morning.

A CCTV camera at the parking area above the cottage recorded the image of a female figure in a light coloured skirt said to be Ms Knox (who owned such a skirt, now being analysed), entering the driveway of the cottage at 8.43pm - five minutes after the trace of Mr Lumumba's mobile phone was registered in the area and eight minutes after Amanda sent him the "See you later" text message.

If the image is that of Ms Knox, and if the timing of Ms Kercher's movements is correct, Ms Knox would have been inside the cottage for about half an hour by the time Ms Kercher arrived. It is not yet clear whether the surveillance cameras captured the image of any other figures arriving at the cottage.

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