Page last updated at 17:30 GMT, Thursday, 18 March 2010

Detectives solved murder case using dog DNA

By Rienkje Attoh
BBC News, London

The murder of 16-year-old Oluwaseyi Ogunyemi in south London was solved by the science of genetic profiling but not of a human killer - instead it was used to single out two dogs.

Oluwaseyi Ogunyemi
Oluwaseyi Ogunyemi was stabbed in the chest and abdomen

No murder weapons were ever found.

However, scientists used DNA profiling to prove that samples collected during the investigation were a billion times more likely to come from two specific dogs than any other animals.

The results conclusively linked them to his death.

The dogs used in the attack on Oluwaseyi, who was known as Seyi, were an adult male pit bull-mastiff cross named Tyson and an adult female pit bull-Staffordshire cross called Mia.

The case was viewed as highly unusual by detectives because in the initial stages of the attack in Larkhall Park, Stockwell, dogs were deployed as weapons before Seyi was repeatedly stabbed and beaten to death in April 2009.

The dogs also received several knife wounds in the attack.

Tyson, who was owned by Chrisdian Johnson, 23, left a blood trail when he and his owner ran away from the scene of the crime.

When police arrested Chrisdian, his victim's blood was on his hands and there was also blood from his dog on his body.

The probability of seeing the same DNA in another dog is less than 1 in a billion
Dr Rob Ogden, Forensic zoologist

Saliva from the other dog Mia, owned by Darcy Menezes, 18, was discovered on torn clothing found in the park.

Mr Menezes was cleared of murdering Seyi and the attempted murder of his 17-year-old friend Hurui Hiyabu.

Both had suffered dog bites and were found critically injured in the park. Two others who had been with them were also stabbed.

Forensic zoologist, Dr Rob Ogden, said: "The technique we have is the first one in the UK that allows us to link an individual sample back to an individual dog with a very strong level of certainty.

"It's the first time we've also used the population database we now have for dogs.

"The probability of seeing the same DNA in another dog is less than one in a billion.

"Before we were able to identify the species of dog or species of other animals, this time we can identify which individual dog a sample may have come from.

"We can now match a trace sample, whether it be blood or saliva or hair, back to a dog and we have a level of certainty regarding that so we can say a profile is a billion times more likely to come from one dog than another dog in the country.

"Human DNA profiling is a big thing but where there's not human evidence or sufficient evidence police can now start to use non-human DNA techniques for the same purpose."

Chrisdian Johnson's dog Tyson
Chrisdian Johnson's dog Tyson suffered a neck wound

According to the scientists, dog DNA profiling cannot provide "categorical proof" that a human was at the scene of the crime but it can provide "very strong evidence".

"For example, if it was someone's pet and if the pet has been in a place and has left hair or left saliva then linking that pet to the owner who may be a suspect can be very clear evidence," said Dr Ogden.

It is believed Seyi was a victim of a revenge attack carried out by members of a rival gang.

A police investigation revealed two groups, each of about six youths and aged between 15 and 20, had been in the area of the Lansdowne Green estate on the evening of the attack.

The two gangs had been "patrolling" the estate before merging to form the "attacking group" at the entrance to the park

Witnesses heard shouts of "Get him, get him" and saw Seyi with his friend Hurui running down a pathway.

Seyi tried to climb over a fence to escape but one of the dogs dragged him down, shortly after the gang caught up.

He died at the scene after being kicked and punched, then stabbed six times.

Hurui was stabbed nine times but survived.

The attack was described by one shocked onlooker as mirroring the behaviour of a pack of wild animals.

Witnesses said gang leader Chrisdian Johnson moved from victim to victim stabbing them, while other members of the gang kicked and punched them.

Chrisdian Johnson was found guilty while his brother Shane was cleared of all charges.


CCTV pictures showed the gang moments after the attack

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