A forensic scientist has told a murder trial jury that there was no evidence lighter fuel was squirted through the letter box of a pub to start the fatal blaze that killed the licensee.

Sarah Thrippleton Hall, 37, was asleep when Jason Hall lit the fire at the Chevin Inn at Menston that claimed her life on Good Friday.

Hall, 34, has admitted responsibility for his estranged wife's death but claims that he only lit a small fire on the outside of a door that he thought would burn itself out. Instead the fire took hold of the hallway and stairs blocking Miss Thrippleton Hall's only escape. Her body was found in a bedroom next to a closed window. She had died from smoke inhalation.

Giving evidence at the trial at Bradford Crown Court, fire examiner Dr Gordon McKinley said the seat of the fire was in the hallway, but he added that it was not possible to say conclusively if it had been started from the outside of the front door or the inside.

The prosecution has put forward the possibility that Hall squirted lighter fuel through the letter box which he then lit. But, when cross-examined by Hall's barrister Michael Harrison QC, Dr McKinley said that forensic tests found no evidence accelerants had been used.

He added: "If the door was tight-fitting against the aluminium threshold strap ... I consider it very unlikely that the flames could have the ignited carpet at this point.

"However if there was a significant gap between the door and the front face of the threshold strap I cannot exclude that the flames could have ignited the carpet."

Hall, of Scotton Grove, Knaresborough, has already pleaded guilty to his wife's manslaughter but denies murder.

The trial has been told that the couple had bought the pub around the time of their marriage in 2003. The volatile and sometimes violent relationship did not last and Hall moved out in an acrimonious split in May, 2005.

The jury have been told that he had become upset by the fact that Miss Thrippleton Hall was still living in the pub. He had told friends that he would "burn the pub down" although they have told the court that they thought that he was joking and considered his remarks nothing more than a flippant comment.

The trial continues.