A jury must decide why Michael Humphries came into Oxford on the day he is alleged to have murdered Dr Barbara Johnston and if he had time to carry out the murder, said a judge.

Humphries, 43, of Ferndale Street, Faringdon, has denied stabbing, beating, strangling and suffocating Dr Johnston, 55, in her flat in Woodstock Close, Oxford, in January.

Judge Anthony King, summing up the prosecution case, described how Humphries was said to have driven into Oxford in a hired van on January 24.

The jury spent four hours deliberating on Friday but did not reach a verdict and will return to the court on Monday.

The jury has been told a van Humphries hired was seen on CCTV at the BP garage at the Wolvercote roundabout in Oxford. Dr Johnston's bank card was used to withdraw £200 at a cash machine there. The judge said: "The prosecution say Barbara Johnston was alive at 11.37pm on Monday, January 23. She logged on to a computer and had spoken to her parents. At 9.59 the following morning she switched on her computer again using her personal password. She was dead by 10.55am, when her card was used at the BP garage. She and her car were not seen at the BP garage."

Judge King said Humphries had been at Cumnor Hill at 10.05am that day, and would have been in Woodstock Road by 10.20am. He asked the jurors to consider what happened between 10.20am and 10.55am and whether Humphries would have had time to get into the flat and cause Dr Johnston's death, before heading to the garage.