Ian Huntley's explanation of how Holly Wells and Jessica Chapman died in his bathroom was dismissed by a senior Home Office pathologist yesterday.
Dr Nathaniel Cary told the Old Bailey that while the decomposed state of the bodies meant he could not rule out Mr Huntley's claim that the girls had died in a sequence of events on pathological evidence, he had never heard of such a case.
The defendant claimed that the girls had been invited into his bathroom after Holly had a nosebleed. She was found dead in the water after he had reached out and covered the screaming Jessica's mouth, the court was told.
Going through each strand of Mr Huntley's statement, Dr Cary said he would usually associate drowning in bathrooms with someone who was severely intoxicated, suffered from fits or had been forcibly held down. Mr Huntley claimed that Holly drowned after being immersed in a bath he had run for his dog.
Dr Cary questioned why neither the defendant nor Holly's best friend had simply pulled her out, adding: "I am not aware of a previous case where it is suggested that somehow someone is drowning in a bathroom in the presence of two other persons."
Without being rotated, a 10- year-old falling back into the bath would most likely have become wedged between the back wall and sides. The bath overflow was at a height of 11 inches, he continued, making it impossible for there to be seven more inches in it, as claimed by Mr Huntley, unless it was blocked.
"How would her legs get over the edge of the bath if she simply fell backwards? Were the legs in fact lifted over to get her more into the bath?" he added.
A nosebleed, he said, would most probably have dripped on Holly's clothes or the surrounding area, yet sophisticated forensic science tests had found none. Even immersion in a bath would have "contaminated" the clothing.
Turning to the death of Jessica, he said: "This was a fit, conscious young girl and, in my view, the only way in which she could have been smothered to death would have been through force against vigorous struggling."
Pointing out that it would be difficult to smother someone standing up, he said an assailant would have to keep a hand over the mouth after collapse. "I find it wholly implausible that Jessica could somehow be smothered to death in an upright posture," Dr Cary said. The trial continues.