A law student accused of killing the doctor acting as his guardian "snapped" because of exam pressure, a jury heard.
David Quartey, 22, of Humber Road, Dartford, Kent, denies murdering consultant paediatrician Dr Victoria Anyetei, 54, on 14 August 2007.
The court heard the doctor, who worked at St Thomas's Hospital, London, was found inside her car which was on her driveway. She had 56 stab wounds.
She had discovered Mr Quartey had lied about his course, the jury was told.
Outlining the case for the prosecution, Anthony Haycroft told Maidstone Crown Court Mr Quartey was living with Dr Anyetei, who was separated from her husband, and her son Andrew Thompson at their home in Teynham Road, Dartford at the time.
'Lost control'
He had failed exams at the Kensington Business College for a second time and had tried to hide this from her, Mr Haycroft said.
Quartey, the son of a High Court judge in his native Ghana, had become friends with Dr Anyetei after she had saved the life of a member of his family, and had been living with her since October 2005.
The jury heard that Mr Quartey, whose one-year law foundation course cost £14,000 a year, was a "normal, placid, likeable young man" but had a poor attendance record and had failed his exams twice, putting his visa in jeopardy.
Mr Haycroft said: "He lied to Dr Anyetei about his studies. We say matters came to a head when she found out the truth and it was on that Tuesday August 14 that we say he snapped and lost control."
The court heard that Mr Thompson, 21, told police afterwards that his mother had told him just hours before she died that Mr Quartey was "scaring her."
Mr Haycroft said relations between Mr Quartey and Dr Anyetei, whom he called "mum" or "mother", had been strained after his lies were discovered.
Forensic evidence
Dr Anyetei, a devout Christian, had arranged to meet his tutors and told him she would chaperone him into London to ensure he attended classes from 13 August.
CCTV evidence shows Dr Anyetei drove Mr Quartey to Dartford train station that day, and they both got on a train into central London, her usual route to work.
The court heard Mr Quartey then travelled back to Dartford and met up with a friend.
The following day, Dr Anyetei planned to take Mr Quartey to the station again but, Mr Haycroft said, instead he stabbed her to death.
The jury heard forensic evidence indicated Mr Quartey was responsible and had covered her mouth while she struggled.
The murder weapon, believed to be a single-edged knife no more than six inches long, was never found.
Dr Anyetei held a British passport and had been living in the UK for around 13 years.
The trial continues.
