The killer of Billie-Jo Jenkins might not have been spattered with any blood on the front of his clothing, the Old Bailey has heard.
Defence witness Professor David Dennison told how he carried out experiments using a football filled with water and doused in blood.
An assistant was told to attack the "head" with up to eight strikes of a metal pole to reveal the pattern of any spray.
But in several trials the researcher was found to have few or no bloodspots on her arms and legs.
Professor Dennison, who has advised the Royal Navy, Ministry of Defence and Health and Safety Executive, said: "One of the things we learnt was we did get very little spatter on the front."
Prosecutor Nicholas Hilliard claimed this confirmed the view of a Crown expert.
He added: "It is possible to carry out an attack of this kind and get very little blood on you."
Prof Dennison replied: "That was one of the findings. We could get barely any on the front.
"It supports the idea that it is possible to attack somebody and not get any on the front."
Former deputy headteacher Sion Jenkins, 47, allegedly battered his 13-year-old foster daughter to death with an iron tent spike at their home.
The prosecution say blood spatter invisible to the eye was sprayed on his jacket and trousers during the attack on February 15, 1997.
But the defence claim air trapped in Billie-Jo's lungs may have caused the spray when Sion Jenkins went to comfort her on the floor.
Jenkins was convicted of murdering Billie-Jo at the family home in Lower Park Road, Hastings, and jailed for life in 1998. He is now facing a retrial ordered by the Court of Appeal.
It is claimed he was on edge because he had lied in his application for the headteacher's job at William Parker School in Hastings.
Jenkins claimed he got ten grade-A O-levels from Gordonstoun College in Scotland when he had only two passes and had never been to the school. He also said he was qualified to teach English but only had a PGCE in PE from Nonnington College in Canterbury, Kent.
Jenkins, whose parents live near Aberystwyth, south Wales, has since married Christina Ferneyhough, 55, a divorcee and former school deputy headteacher.
The millionairess, who lives in a £1.5 million mews house in Groom Place, Belgravia, central London, originally comes from Portsmouth, Hants, and has been at court every day.
Jenkins, who was born in Greenwich and later educated in Gloucester and Glasgow, denies murder on February 15, 1997.
The trial continues.
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