Antoni Imiela denies nine counts of rape and one of abduction

Antoni Imiela, 49, denies nine counts of rape involving women and girls.

Dr James Walker said the chance of DNA from anyone unrelated to Mr Imiela matching the profile of the girl's attacker was "probably in excess of hundreds of billions" to one.

The figure of one in one billion given by the prosecution was "conservative".

Imiela, a former railway worker from Appledore, near Ashford in Kent, also denies the kidnap, indecent assault and attempted rape of a 10-year-old girl in Birmingham.

'No major flaws

Dr James Walker told the court he had checked the results of DNA tests done by the Forensic Science Service (FSS).

He reported the findings to Mr Imiela's defence team but said he was unable to make his own comparison because the "crime" sample from the 10-year-old girl had "deteriorated" in the two years since the attack.

But under cross-examination, Dr Walker said he found no major flaws with the work of the FSS which he said was of the highest standard.

Mark Dennis, prosecuting, asked him about the one in a billion figure from the FSS in relation to the attack on the 10-year-old girl in Ashford.

Mr Dennis said: "You do indicate that actually it is not the true figure calculated.

"I take it that is because the true figure is much larger than one in one billion."

Dr Walker said: "It is probably in excess of hundreds of billions."

He agreed that a figure of one in one billion suggested there were only three men in the world who would have DNA matching a profile of the girl's attacker.

The case continues.