A 22-year-old man who repeatedly stabbed a teenage boy was facing life in jail today after the first case in which new dog DNA technology was used in a murder prosecution.
Seyi Ogunyemi, 16, was stabbed to death in a "vicious" attack by a gang of youths said to have acted like a "pack of wild animals" as they set upon him and his friends.
The murder by Chrisdian Johnson, 22, was described in court as unique because dangerous dogs were used as weapons to savage their victims before they were knifed.
One of the animals, called Tyson, brought down and mauled slightly-built Seyi as he tried to escape from his pursuers over a fence.
The boy stood no chance once he was in the dog's ferocious grip and was then stabbed six times by its owner Johnson.
Johnson was arrested as he fled from the scene of the murder last April, bare-chested and covered in blood.
New technology, used for the first time, proved by a billion-to-one probability that some of the blood came from his dog Tyson, which had been knifed during the melee. The rest was shown to come from the teenage murder victim.
Police hailed the dog DNA technique, which had just been developed at the time of the murder, as a "hugely powerful investigative tool".
Johnson, of Wyvil Road, south Lambeth, south London, who had been allowed to keep the dangerous dog only when a court imposed strict conditions on his ownership in late 2007, was today found guilty of murder.
He was also convicted of the attempted murder of the victim's 17-year-old friend Hurui Hiyabu, said to have been lucky to survive after he was knifed nine times.
Johnson's brother Shane Johnson, 20, of the same address, was cleared of both charges.
A third defendant, 18-year-old Darcy Menezes, of Studley Road, Clapham, south London, was cleared earlier during the trial.
The court heard that his dog, a female adult brindle Staffordshire terrier called Mia, also took part in the attack, but a judge ruled there was insufficient evidence to show Menezes was involved.
A decision on whether to destroy the dogs has not yet been made.
The convictions come shortly after Home Secretary Alan Johnson announced new measures designed to tackle the problem of dogs being used as weapons.
Johnson was remanded in custody and will be sentenced tomorrow.
Seyi was killed when he and his friend were set upon by a large group of youths aged 15 to 20 and two dogs in Larkhall Park, south London, the court heard.
Tyson, an adult male Staffordshire bull terrier-bull mastiff cross was used to bring him to the ground before he was knifed.
Doctors performed emergency surgery at the scene to try to save Seyi's life but he died from a wound to his aorta.
Brian Altman QC, prosecuting, told jurors: "What was so unusual if not unique about this case is that in the initial stages of the attack both these dogs were deployed as weapons.
"At the time of the attack both dogs were unleashed, and chased and then brought down and savaged their victims, giving their human masters an advantage, enabling them then to access their victims in order to stab them with knives."
One witness said the behaviour of the youths in the attack was "vicious" and "mirroring the behaviour of a pack of wild animals", Mr Altman told jurors.
Another described how he had heard screaming and someone shouting "get 'em, get 'em" before seeing a group of ten to 15 youths wearing bandanas round their faces and hoods up.
New DNA analysis was used to link Tyson's blood to the murder and saliva found on a piece of trouser leg torn from one of Seyi's friends matched Mia's profile.
The same technique also proved that trails of blood at the scene and blood found on Hurui Hiyabu, came from Tyson.
Detective Inspector Mick Norman said: "It's been a hugely powerful investigative tool for us."
Police said Chrisdian Johnson had previously been given a specific exemption by a court to keep Tyson despite being a dangerous dog by breed.
He agreed to have him chipped, tattooed and insured but further conditions meant the animal should have been kept on a lead and muzzled at all times in public.
After he was stabbed in the attack on Seyi, Tyson was taken by taxi to a Blue Cross animal hospital where he was found by police. Chrisdian Johnson's other dog, Chrome, of the same breed, was at home on the night.
Mr Altman told the court that others clearly took part in the apparently gang-related attack on a rival group but have not been identified or caught "despite a thorough police investigation".
The knife used to kill Seyi has not been recovered.
Mr Norman said the case was "unique" because of the way dogs had been used as weapons in a murder.
He added: "When you mix a dog and then knives you have got a really lethal combination as in this case."
Police said Mia, the other dog alleged to have been at the scene of the murder, had been involved in an attack on an 11-year-old boy in June 2008, when his owner accidentally lost control of him.
The victim was taken to hospital suffering from dog bites and the incident was reported to police but no further action was taken.
Officers at the Met's dangerous dogs unit have seized more than 1,000 in the past year and say the numbers in London are soaring, with the problem fuelled by gang culture and insecurity.
Following the verdicts, Mr Norman said that Seyi "didn't stand a chance" during the attack.
He said police would be applying for a destruction order for Johnson's dog Tyson but was unable to comment on the future of the other dog, Mia.
Speaking outside court, the detective said: "I would like to say on behalf of the family that even though this verdict won't bring their son Seyi back, I feel that it will give them some sense that a justice verdict was returned.
"This was an investigation which was difficult and also complicated to some degree by the fact that dogs were used as weapons.
"Seyi Ogunyemi was a young man of slight stature, suffering from Crohn's disease.
"He was attacked by a dog released by Chrisdian Johnson and taken to the ground. While on the ground, he was stabbed where he lay. He didn't stand a chance.
"However, taking advantage of new scientific techniques, we were able to link the dog used in the attack to the scene, to the victim, and to Chrisdian Johnson.
"The message I'd like to reinforce is that if a dog is used as a weapon, you will be caught, you will be prosecuted, and you will be convicted."
He added: "At the present time, the dogs remain with the police. We will be applying for a destruction order in relation to the dog belonging to Chrisdian Johnson."