A FIVE-DAY delay between the death of Poppi Worthington and her post mortem could have affected the validity of its results, a third expert pathologist told an inquest.

Dr Liina Palm, a paediatric histopathologist from Great Ormond Street Hospital in London, was asked to review the findings of the examination on the tragic tot by the National Crime Agency.

She told a hearing - launched to establish how the 13-month-old died five years ago - that some marks found on Poppi could be the result of natural changes following her death.

She added this may have "compromised" results from the post mortem undertaken by Home Office pathologist Dr Alison Armour on December 17, 2012.

Dr Palm, who has previously given evidence on the case in the Family Court, said she could not fully exclude a penetrative attack to the little girl.

But the court went on to hear Dr Palm admit that fresh bleeding reported to have "dribbled" or "trickled" from the tot on the morning of her sudden death "needed explaining".

When addressing Dr Palm's interpretation of marks noted on Poppi, Alison Hewitt, counsel to the coroner, said: "What about the possibility of it being caused by trauma?"

"There's a possibility," Dr Palm said.

But she added: "The tissue shows post mortem degradation and I can't jump to this conclusion without considering these post mortem changes."

Gillian Irving QC, representing Poppi's mother, repeated evidence already heard by the inquest - that Poppi had woken up screaming at around 5.45am on the morning she died.

Her father came downstairs to get a new nappy for her, the proceedings have been told, before returning a short time later with Poppi in his arms, not breathing.

"It's a very rapid death isn't it?" Mrs Irving asked.

"That raises the finger of suspicion doesn't it?"

Dr Palm replied: "Well, it needs to be explained."

Mrs Irving went on to ask Dr Palm to confirm that the expert had been unaware that some of the police officers who provided information to her about Poppi had been under investigation by the Independent Police Complaints Commission at the time.

"I think that may have been the case," Dr Palm replied.

The inquest has heard from Home Office pathologist Dr Nat Cary, who was commissioned by Cumbria police to provide a second opinion on the findings of a post mortem carried out on Poppi.

He said he had seen no evidence that the little girl had been a victim of a sexual assault.

This is at odds with the conclusion of fellow Home Office pathologist Dr Alison Armour, who has concluded Poppi had suffered a "penetrative trauma" before her death.

All three pathologists agree the tot's cause of death is unasertained.

No natural cause has been identified.

Last year, Mr Justice Jackson, now Lord Justice Jackson, ruled in the High Court that Poppi had suffered a serious sexual assault at the hands of her father before she died - an allegation Mr Worthington has always denied.

The inquest, heard by senior coroner for Cumbria David Roberts at County Hall in Kendal, continues.