A blow of ?tremendous? force was needed to break the jaw of one of the Cooper twins completely in two, a court heard yesterday.

Bone expert Professor Heather Walsh-Haney said the u-shaped lower jawbone of Jahmal Cooper would have been ?very strong?.

Asked how easy it would have been to sever, she said: ?It would take a tremendous blow to break?.

The professor added that, in her opinion, the injury would have been caused by a blunt, hard object. It was inflicted at or around the time the 20-year-old died, the court heard yesterday.

Prof. Walsh-Haney, a Florida-based forensic anthropologist, was giving evidence about 20 bone samples she was sent after the remains of the Cooper brothers were discovered nearly 80ft down Abbot?s Cliff last April.

The trial has already heard from pathologist Dr. Valerie Rao who confirmed both twins died from ?multiple blunt force trauma?, probably after a blunt weapon was used and after their bodies were fractured in various places. She claimed the twins might have died minutes after their brutal injuries were inflicted.

Prof. Walsh-Haney ? who echoed a lot of Dr. Rao?s evidence, including her verdict on the causes of both deaths ? said bone samples showed Jahmil had fractured three parts of the back of his neck. She said they were either caused by a blow to the back of the neck, face or to the top of the head.

She also said nose bones had been completely fractured and the right cheek bone had been ?splayed apart?. These injuries could have been caused by a blunt object, the jury heard.

The bone expert then outlined Jahmal?s jaw injury and also said he also had two complete fractures on both forearms. She said an ?extreme? blow was needed to inflict these injuries and said the position of them indicated the victim?s hands had been raised in a defensive position. She added that the blow would have been focussed on the forearms.

The prosecution claim defendant Kenneth Burgess launched a vicious baseball attack on the 20-year-old brothers at a lower apartment on Crown Hill Lane, Devonshire, last March. Co-accused Dennis Alma Robinson guarded the door to prevent escape, the trial has already heard.

Courtenay Griffiths QC, for Burgess, asked Prof. Walsh-Haney if all the skull injuries suffered by Jahmil could have been caused by a single blow. The expert, who has worked on remains from victims of 9/11 and Hurricane Katrina, said this was possible.

Asked the same question about a single blow causing the skull injuries to the other twin, Jahmal, she replied: ?Yes.?

John Perry QC, for Robinson, told the court no rib injuries were found in either victim. He asked if the professor would expect rib fractures to be found if a body fell 78 feet and hit the ground. She said it would be possible, but added that the forearm breaks on Jahmal were more consistent with blocking blows.

A detective involved in the double murder investigation also gave evidence yesterday.

Detective Constable Sylvester Augustine, of the Serious Crime Unit, told the court about clothing and other items seized from the defendants in the period after the twins vanished.

He said on April 12 last year he flew to forensic science offices in Ontario, Canada with items for DNA testing that included Burgess? Tissot watch and a Fubu shirt with suspected blood stains, taken from an upper apartment at Crown Hill Lane on March 15.

On April 20, photographs were seized during a visit to the same apartment. One featured Robinson and another featured Robinson and Burgess.

Under cross-examination by Mr. Griffiths, Det. Con. Augustine said a medical examination on March 15 showed no sign of injuries on Burgess.

The detective said the first item seized in the search of the upper apartment that same day was the stained Fubu shirt and yesterday afternoon?s court session ended with the prosecution objecting to Mr. Griffiths repeating a claim he made earlier in the week that a Police officer had ?planted? that item of clothing in the apartment.

Burgess, 33, of Hamilton Parish, and Robinson, 34, of Southampton, deny murdering the Cooper twins on March 13, 2005.

The trial continues.