Consultant paediatric radiologist Owen Arthurs is first up in the witness box this morning. He's giving expert evidence on CT scans, X-rays and other images in this case

Dr Arthurs published a study in 2015 on the prevalence of air, post mortem, in infants. That study looked at 48 children. Of the 48, six were comparable to this case - but in each of those cases there were clear explanations for the presence of air in vessels

He agreed with prosecutor Nick Johnson that it is 'very rare' to find air vessels without an obvious explanation

We've gone backwards a little in timeline (the expert wasn't able to make it to court earlier), Dr Arthurs is discussing the case of Child E. It is alleged that Ms Letby fatally injected air into the bloodstream of the baby in June 2015

Court is now being shown a radiograph of Child E. Dr Arthurs agrees there is 'no significant abnormalities' present. Prosecutor Nick Johnson asks if an air embolis would show up on such a radiograph

Dr Arthurs says an air embolis is not present and to see it there would have to be 'a lot of air' and the radiograph would have to have been 'done almost immediately' after the injection

Dr Arthurs is now being asked about Child E's twin, Child F, who the Crown say was also attacked by Ms Letby but survived

Dr Arthurs says he can make no real comment on the case of Child F. We're now moving to Child G. Ms Letby is accused of attempting to murder the premature girl three times in September 2015

The prosecution alleges Ms Letby overfed Child G with milk through a nasogastric tube or injected air into the same tube

Dr Arthurs is taking the court through radiographs, taken at Arrowe Park Hospital and the Countess of Chester, of Child G.

Dr Arthurs says 'there isn’t anything specific' to suggest Child G was suffering from sepsis/NEC or any other infection. He said 'there's nothing on the X-rays that would really provide a diagnosis' for Child G's condition

We're now moving on to Child H. Ms Letby is accused of trying to kill the infant on two occasions in September 2015. The prosecution claim she first attacked Child H in the early hours of 26 September and then again the following morning

Jurors previously heard Child H, who was born six weeks premature, needed treatment for a pneumothorax, which occurs when air leaks into the space between the lung and chest wall.

On the evening of 24 September 2015, Dr Alison Ventress inserted a pigtail chest drain to prevent any accumulation of air within the chest. However, in the early hours of 25 September more air had accumulated a second drain was inserted

Ms Letby's defence counsel Ben Myers KC previously claimed that Dr Ravi Jayaram inserted the second drain in the "wrong place". Dr Arthurs is now going over the X-rays of Child H which show the drains

Dr Arthurs notes that the position of the drains have moved, but he says that the 'precise location isn’t really critical if it’s having the desired effect if it’s draining the pneumothorax' - essentially supporting what Dr Jayaram has previously said here https://www.bbc.co.uk/news/uk-...

Dr Arthurs is now moving on to Child I. Ms Letby is accused of injecting air into her stomach via a feeding tube

Dr Arthurs has said there is evidence of pneumatosis (gas within the wall of the small or large intestine) on an X-ray from 30 September of Child I

Dr Arthurs has said Child I had a 'normal' bowl, as per her X-ray on 18 October and into 20 October. Looking at an X-ray from 23, there is a 'massive' dilatation of the stomach

Dr Arthurs says it is 'quite unusual to see babies with this degree of dilatation of the stomach', he says it can cause 'splits in the diaphragm' and that can lead to 'respiratory complications'

Asked how much air it would take to generate such images, Dr Arthurs said: 'We don’t know, I don’t think anybody really knows. Those experiments can’t really be carried out, we can’t experiment on babies giving them 50 or 100mls of air and taking x-rays'

He adds: 'I would guess more than 20mls of air' He is asked, in the absence of another explanation, whether 'someone has deliberately injected air' Dr Arthurs says 'I think that stands to reason'

We're back after a break for lunch. Ben Myers KC, defending, is now questioning Dr Arthurs

He's asking Dr Arthurs about Child H and the positioning of her chest drains. Mr Myers asks if he is aware of guidelines on where chest drain should be inserted, in terms of the intercostal space

Dr Arthurs says that the guidance, to which Mr Myers is referring, 'refers to where they go in terms of the chest wall, not where they are inside chest'

Dr Arthurs accepts that a neonatologist is better placed to comment on positioning of drains and clinical impact

Mr Myers is now moving on to Child I. He put it to Dr Arthurs that from X-rays alone it was "not possible to establish a precise cause" of the air being present, Dr Arthurs agreed

Registrar Dr Rachel Chang, who was on shift the night Child I died, is next in the witness box

Dr Chang is being asked about the events of midnight, 22 October 2015. She tells the court she 'cannot remember' how she was alerted to Child I's crash, but she is reading out her notes from that night

Dr Chang said when she was bleeped she would have perceived that as a 'medical emergency'. Her notes show that when she arrived Child I was being manually ventilated