A sixth-former murdered her boyfriend with a steak knife during an apparently motiveless argument after a night out celebrating her A-Level success, a jury heard today.
Katherine McGrath, 19, of Brackla, Bridgend, south Wales, plunged the knife in the heart of boyfriend Alyn Thomas, 22, in a single thrust which proved fatal, the court was told.
Roger Thomas QC, prosecuting, said that McGrath later claimed she had inadvertently killed her boyfriend as she defended herself against his unexplained violent attack.
McGrath today went on trial at Cardiff Crown Court, where she denies a single charge of murder.
Mr Thomas, of Cymmer, near Neath, died on the kitchen floor at McGrath's detached family home in the early hours of August 21 last year.
"There were no witnesses to this incident and the only account of what actually happened comes from the defendant," Mr Thomas said.
"We submit that essential parts of that explanation are misleading, and that there is no justification for taking hold of what was a weapon, a steak knife, and using it to kill Alyn Thomas.
He advised the jury to "exercise caution before you accept the explanation that she subsequently made".
Mr Thomas said McGrath told police her boyfriend had attacked her for no reason.
Both had been drinking during an evening in Bridgend and returned to her home by taxi and had decided to eat a frozen pizza.
After fetching it from the freezer, McGrath was to claim that her boyfriend underwent a "sudden and dramatic change", Mr Thomas said.
She claimed that he shouted out the name "Carris" and then pushed her back on to the settee in the adjacent living room.
There had been no previous indication of an argument, no anger or shouting.
Mr Thomas said she claimed her boyfriend "came towards her very, very quickly and with an angry expression on his face".
The jury heard McGrath had claimed her boyfriend spat in her face and pushed her down when she tried to stand up.
Mr Thomas said she went on to explain that he raised his hand to her and she did the same to defend herself, at which point she said he gripped her right hand and bit her thumb.
Mr Thomas said that McGrath subsequently gave the police different versions of how she came to get out a steak knife.
She told police "she was scared and in complete agony because Alyn Thomas had her thumb in his mouth and was biting it".
She said that while this was happening they had moved "two steps" into the kitchen where she could reach a draw containing knives.
While still at the scene after the death, she had told police "my initial thought was to pull out a knife to scare him".
Mr Thomas said that when she gave a police statement she said what amounted to: "I was just feeling around for whatever came into my grasp and it was just bad luck that it was a knife."
He said that she had also revised the description of where she was standing in the kitchen to make her story more plausible.
"According to her, at this stage his face had a horrible expression on it."
She insisted that her intention had only ever been to "scare him" with the knife.
Mr Thomas said that as the argument continued "she saw, she says, a mark on his skin like a scratch and threw the knife away.
"I saw him stumble for a few steps and fall back," she told police.
He said that McGrath called the emergency services in a distressed state and "begged for assistance".
When police arrived she told them that he had pushed her to the floor, and that he had two assault convictions.
The couple, who had been together for a year, had gone to Brynteg secondary school to get her A-Level results the day before.
McGrath was due to go on to university and had spent the rest of the day looking for a place using the university clearing system.
Mr Thomas was on a gap year from college and was working at a local Tesco store.
The couple had visited a number of pubs and clubs in Bridgend and had both been drinking into the early hours.
But a taxi driver who took them back to Brackla an hour before the death described them as "a lovely couple" and said neither was particularly drunk.
The case continues.