An art student stabbed to death while babysitting two young children met her accused killer via Facebook, before starting a "secretive" relationship with him, a court heard today.

Katie Wynter, aged 19, was stabbed 13 times in the stomach and abdomen at her sister's home in Beech Drive, Borehamwood, Hertfordshire on Boxing Day night, while looking after her niece and nephew.

She was discovered dead the following morning by her mother in a pool of blood. Both children were in the house at the time, but were unhurt.

Her boyfriend Tony Bushby, aged 19, of Digswell Close, Borehamwood, denies murder.

Fellow student Kien Minh Voong, who studied with Katie at West Hertfordshire College, described to the jury how her friend fell in love with Bushby after meeting him on Facebook, and would travel to a clearing in a secluded wood in Borehamwood to meet with him.

A second college friend, Jasmine Mandata, added that Miss Wynter was shy about the "secretive" relationship, and rarely discussed it.

Miss Wynter was studying a two year foundation degree course in illustration at the college's School of Art and Design in Watford, where Bushby also studied until June 2011. However, the pair shared no classes and friends said they never saw the two together.

She had been due to complete her degree course last month.

Miss Voong added: "She said she met Bushby on Facebook.

"She told us she loved him but she seemed shy about it.

"I didn't get the impression she saw much of him, she contacted him primarily through Facebook, phone calls and texting.

"She would always say the relationship was fine if I asked, but she didn't talk about it much.

"She said she would meet him in this place in the forest in a clearing and just talk and kiss."

Bushby was arrested on the day Miss Wynter's body was discovered. He told police he had spoken to her the previous night as he walked home and she had told him she was babysitting.

The jury was shown Bushby's mobile phone, which had a damaged screen and SIM card when it was recovered by police. Mr Michael Speak, prosecuting, claims it was done intentionally.

A mobile phone forensic expert told the court it was impossible to say how the damage had occurred.

The court also heard how Bushby was a black belt in karate and had expected to go on to become an instructor.

Michael Hollingbery, the owner of Orca Kai Karate Club in Borehamwood, who taught Bushby, said:"I saw him turn from a boy into a man. He had a passion for karate which came from his heart.

"He was never aggressive or violent, and I was astounded when I found out (about his arrest). I just this thought "this is the wrong character."

In a statement read out in court Emma Duree, a director at West Herts College, described Miss Wynter as a hardworking, model student and added: "Her tutors said she was polite and a pleasure to teach."

Friends spoke of Miss Wynter's shy nature, describing how she regularly attended church and babysat for her sister's children, and didn't drink or go out partying.

Childhood friend Sheridan Skinner told the court: "I don't know why any of this would happen. She was a lovely girl and, in the whole time I knew her, we never argued."

The trial continues.